Technical FAQs for PHP and SEO Beginners

On This Day In History 16 November

2021-11-18T08:35:00.001-08:00

What happened on November 16 in the history of India and the world?

Famous events, birth anniversaries, and death anniversaries today, November 16 in Indian and world history.

Historical events in Indian and world history on November 16

International day for tolerance

1849, 16 November: World famous Russian writer Fyodor Dostoevsky was sentenced to death for being a member of an underground organization.

1868, 16 November: Scientists Lacier and Nansen discovered helium by studying a total solar eclipse. It is named after the Greek sun-god Helios.

1893, 16 November: Dr. Annie Besant arriveed in India.

1907, 16 November: Oklahoma became the 46th state of the United States.

1914, 16 November: US Federal Reserve opened.

1915, 16 November: Vishnu Ganesh Pingale, accused in the Lahore conspiracy, and seven others, including Bagi Kartar Singh, were hanged.

1938, 16 November: Albert Hofmann’s invention of the lysergic acid diethylamide drug came into existence.

1945, 16 November: UNESCO was established.

1988, 16 November: Benazir Bhutto became Pakistan’s prime minister.

1997, 16 November: Swaraj Paul, a non-resident Indian entrepreneur, was awarded an honorary doctorate by the Bradford University, UK.

2013, 16 November: After a long career of 24 years, the great cricketer Sachin Tendulkar retired from cricket and within a few hours, he was declared the Bharat Ratna, the highest civilian award in India. He got this honor at the youngest age (40).

Famous birthdays on this day – November 16 in Indian history

Famous birthdays of the people in India and the world on this day – November 16

42 BC: Tiberius, the second Roman emperor.

1846: Akbar Allahabadi, an Indian Urdu.

1896: Oswald Mosley, 6th Baronet, a British politician.

1897: Choudhry Rahmat Ali, a Pakistani nationalist.

1909: Hāfiz Mirza Nasir Ahmad, the third caliph, head of the Ahmadiyya Community.

1904: Nnamdi Azikiwe, Nigeria’s first president.

1927: Shriram Lagoo, an Indian film, and theatre actor.

1930: Mihir Sen, an Indian long-distance swimmer, and businessman.

1936: Ramoji Rao, an Indian film producer, and media entrepreneur.

1942: Sam Pitroda, an Indian telecom engineer, inventor and entrepreneur.

1946: Terence McKenna, an American ethnobotanist.

1963: Meenakshi Seshadri, an Indian actress, model, and dancer.

1973: Pullela Gopichand, a former Indian badminton player.

Death anniversaries of famous people on this day – November 16

Death anniversaries of famous personalities on this day on November 16.

1240: Ibn Arabi, an Arab Andalusian Muslim scholar, mystic, poet, and philosopher.

1797: Frederick William II, King of Prussia.

1915: Vishnu Ganesh Pingale, accused in the Lahore conspiracy, and seven others, including Bagi Kartar Singh, were hanged.

1947: Giuseppe Volpi, Italian businessman, and politician. He was the founder of the Venice Film Festival.

1950: Dr. Bob Smith, an American physician, and one of the founders of Alcoholics Anonymous.

1960: Clark Gable, American actor.

1967: Roshanlal Nagrath alias Roshan, Indian musician.

1973: Alan Wilson Watts, a British writer, and speaker.

2006: Milton Friedman, an American economist. He received the Nobel Prize in Economic Sciences.

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Latest PHP Technical Interview Questions & Answers for Freshers

2015-12-26T00:13:00.001-08:00

What is the latest current version of PHP?
php 5.3

What are the differences between GET and POST methods in form submitting?
On the server side, the main difference between GET and POST is where the submitted is stored. The $_GET array stores data submitted by the GET method. The $_POST array stores data submitted by the POST method.
On the browser side, the difference is that data submitted by the GET method will be displayed in the browser’s address field. Data submitted by the POST method will not be displayed anywhere on the browser.
GET method is mostly used for submitting a small amount and less sensitive data.
POST method is mostly used for submitting a large amount or sensitive data.

Explain the different types of errors in PHP.
Notices, Warnings and Fatal errors are the types of errors in PHP

Notices:
Notices represents non-critical errors, i.e. accessing a variable that has not yet been defined. By default, such errors are not displayed to the user at all but whenever required, you can change this default behavior.
Warnings:
Warnings are more serious errors but they do not result in script termination. i.e calling include() a file which does not exist. By default, these errors are displayed to the user.
Fatal errors:
Fatal errors are critical errors i.e. calling a non-existent function or class. These errors cause the immediate termination of the script.

What are the differences between require and include?
Both include and require used to include a file but when included file not found
Include send Warning where as Require send Fatal Error .

How to find current date and time?
The date() function provides you with a means of retrieving the current date and time, applying the format integer parameters indicated in your script to the timestamp provided or the current local time if no timestamp is given. In simplified terms, passing a time parameter is optional - if you don't, the current timestamp will be used. Where as time function returns current Unix timestamp.

How can we get second of the current time using date function?
$second = date("s");

How to increase the execution time of a php script?
To Change max_execution_time variable in php.ini file .By Default time is 30 seconds.
The file path is xampp/php/php.ini if xampp software is using.

What does a special set of tags do in PHP?
In PHP special tags the use of this Tags are The output is displayed directly to the browser.

What is meant by nl2br()?
Inserts HTML line breaks (
) before all newlines in a string.

What is use of header() function in php ? What is the limitation of HEADER()?
In PHP Important to notice the Limitation of HEADER() function is that header() must be called before any actual output is send. Means must use header function before HTML or any echo statement

There are Number of Use of HEADER() function in php like below
1> The header() function use to sends a raw HTTP header to a client.
2> We can use header() function for redirection of pages.
3> Used to refresh the page on given time interval automatically.
4> To send email header content like cc, bcc , reply to etc data and lot more

How can we know the total number of elements of Array?
sizeof($array_var)
count($array_var)
If we just pass a simple var instead of a an array it will return 1.

Different Types of Tables in Mysql?
There are Five Types Tables in Mysql
1)INNODB
2)MYISAM
3)MERGE
4)HEAP
5)ISAM

What is the maximum length of a table name, a database name, or a field name in MySQL?
Database name: 64 characters
Table name: 64 characters
Column name: 64 characters

What is the difference between the functions unlink and unset?
unlink() deletes the given file from the file system.
unset() makes a variable undefined.

How can we convert asp pages to PHP pages?
There are lots of tools available for asp to PHP conversion. you can
search Google for that. the best one is available athttp://asp2php.naken.cc./

How can we set and destroy the cookie in php?
By using setcookie(name, value, expire, path, domain); function we can set the cookie in php ;
Set the cookies in past for destroy. like
setcookie("user", "sonia", time()+3600); for set the cookie
setcookie("user", "", time()-3600); for destroy or delete the cookies;

How to create PHP web service with JSON respond? For Android, Iphone or Web Application.

2015-04-27T01:37:00.000-07:00

There is a list at the official PHP website: http://www.php.net/manual/en/refs.webservice.php You can see that PHP can work with OAuth, SCA, SOAP, Yar and XML-RPC. But there is another way which is so simple to create a webservice. It is JSON.

I will show how to create a simple web service with JSON. Our service will get the parameters by using $_GET , therefore we will put the parameters to url. For instance http://mywebserviceurl.com?s=myparameter , so the service will answer depending on myparameter.

Lets look at service's index file:

index.php

<?php

include('connectdb.php');

$something = $_GET['s'];
$sqlcode = mysql_query("Select $something from mydb limit 5 ");

$jsonObj= array();
while($result=mysql_fetch_object($sqlcode))
{
$jsonObj[] = $result;
}

$final_res =json_encode($jsonObj) ;
echo $final_res;

?>

connectdb.php

<?php
    $hostname="localhost";
    $username=""; //write your username
    $password=""; //write your password
    $db_name=""; //write your db name
    $con=mysql_connect($hostname,$username,$password);
    mysql_select_db($db_name,$con) or die ("Cannot connect the Database");
    mysql_query("SET NAMES 'utf8'",$con);

?>

Thats all. You will see the JSON results on the screen. You can validate the JSON results with the help of some sites. Json validator addresses:

http://jsoneditor.net/
http://jsonlint.com/

How to get results of a web service?

Your application will ask this webservice something, then the service will give response with a json result. Your application should get the results with a reader to read the webservice's output.

In PHP, you can do that with file_get_contents() function. Here is an example of my php application:

readwebservice.php
<?php
$jsonObj = file_get_contents('http://mywebserviceurl.com/?s=myparameter');
$final_res = json_decode($jsonObj, true) ;
var_dump( $final_res );
?>

In Android, you can use JSONParser.java which you can find the whole codes at the following topic below. You can simply use jsonParser.getJSONFromUrl() function to read the results. Here is example:

UserFunctions.java

import java.util.ArrayList;
import java.util.List;
import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;
/**
* function make webservice Request
* @param myparameter
* */
public JSONObject loginUser(String myparameter){
String webserviceURL = "http://mywebserviceurl.com/";
JSONParser jsonParser = new JSONParser();
// Building Parameters
List params = new ArrayList();
params.add(new BasicNameValuePair("s", myparameter));
JSONObject json = jsonParser.getJSONFromUrl(webserviceURL, params);
// return json
// Log.e("JSON", json.toString());
return json;
}

Thats all for a simple webservice example. Lets look at an complex example now.

PHP LOGIN WEBSERVICE AND HOW TO USE IT IN ANDROID APP

If you want to create more complex webservices, I am gonna give you an example which is for "login" control. (If you want to look at my source files, you can download full "PHP Login Webservice" from https://sourceforge.net/p/phploginwebservice/)

Put the php web service codes into a directory which name is "android_login_api", so you can reach the web service via "http://mywebserviceurl.com/android_login_api/" url link. Also you should create another directory for other web service needs like "search" or "post" etc. By this way, you can seperate the service codes in a logical manner.

In web service with PHP:
index.php (Web service)

<?php

/**
* File to handle all API requests
* Accepts GET and POST
*
* Each request will be identified by TAG
* Response will be JSON data

/**
* check for POST request
*/
if (isset($_POST['tag']) && $_POST['tag'] != '') {
// get tag
$tag = $_POST['tag'];

// include db handler
require_once 'DB_Functions.php';
$db = new DB_Functions();

// response Array
$response = array("tag" => $tag, "success" => 0, "error" => 0);

// check for tag type
if ($tag == 'login') {
      // Request type is check Login
      $email = $_POST['email'];
      $password = $_POST['password'];

      // check for user
      $user = $db->getUserByEmailAndPassword($email, $password);
      if ($user != false) {
          // user found
          // echo json with success = 1
          $response["success"] = 1;
          $response["uid"] = $user["unique_id"];
          $response["user"]["name"] = $user["name"];
          $response["user"]["email"] = $user["email"];
          $response["user"]["created_at"] = $user["created_at"];
          $response["user"]["updated_at"] = $user["updated_at"];
          echo json_encode($response);
      } else {
          // user not found
          // echo json with error = 1
          $response["error"] = 1;
          $response["error_msg"] = "Incorrect email or password!";
          echo json_encode($response);
      }
} else if ($tag == 'register') {
      // Request type is Register new user
      $name = $_POST['name'];
      $email = $_POST['email'];
      $password = $_POST['password'];

      // check if user is already existed
      if ($db->isUserExisted($email)) {
          // user is already existed - error response
          $response["error"] = 2;
          $response["error_msg"] = "User already existed";
          echo json_encode($response);
      } else {
          // store user
          $user = $db->storeUser($name, $email, $password);
          if ($user) {
               // user stored successfully
               $response["success"] = 1;
               $response["uid"] = $user["unique_id"];
               $response["user"]["name"] = $user["name"];
               $response["user"]["email"] = $user["email"];
               $response["user"]["created_at"] = $user["created_at"];
               $response["user"]["updated_at"] = $user["updated_at"];
               echo json_encode($response);
         } else {
               // user failed to store
               $response["error"] = 1;
               $response["error_msg"] = "Error occured in Registartion";
               echo json_encode($response);
         }
      }
} else {
echo "Invalid Request";
}
} else {
echo "Access Denied";
}
?>

DB_Functions.php (Web service)


<?php
class DB_Functions {

    private $db;

    //put your code here
    // constructor
    function __construct() {
        require_once 'DB_Connect.php';
        // connecting to database
        $this->db = new DB_Connect();
        $this->db->connect();
    }

    // destructor
    function __destruct() {

    }

    /**
     * Storing new user
     * returns user details
     */
    public function storeUser($name, $email, $password) {
        $uuid = uniqid('', true);
        $hash = $this->hashSSHA($password);
        $encrypted_password = $hash["encrypted"]; // encrypted password
        $salt = $hash["salt"]; // salt
        $result = mysql_query("INSERT INTO users(unique_id, name, email, encrypted_password, salt, created_at) VALUES('$uuid', '$name', '$email', '$encrypted_password', '$salt', NOW())");
        // check for successful store
        if ($result) {
            // get user details
            $uid = mysql_insert_id(); // last inserted id
            $result = mysql_query("SELECT * FROM users WHERE uid = $uid");
            // return user details
            return mysql_fetch_array($result);
        } else {
            return false;
        }
    }

    /**
     * Get user by email and password
     */
    public function getUserByEmailAndPassword($email, $password) {
        $result = mysql_query("SELECT * FROM users WHERE email = '$email'") or die(mysql_error());
        // check for result
        $no_of_rows = mysql_num_rows($result);
        if ($no_of_rows > 0) {
            $result = mysql_fetch_array($result);
            $salt = $result['salt'];
            $encrypted_password = $result['encrypted_password'];
            $hash = $this->checkhashSSHA($salt, $password);
            // check for password equality
            if ($encrypted_password == $hash) {
                // user authentication details are correct
                return $result;
            }
        } else {
            // user not found
            return false;
        }
    }

    /**
     * Check user is existed or not
     */
    public function isUserExisted($email) {
        $result = mysql_query("SELECT email from users WHERE email = '$email'");
        $no_of_rows = mysql_num_rows($result);
        if ($no_of_rows > 0) {
            // user existed
            return true;
        } else {
            // user not existed
            return false;
        }
    }

    /**
     * Encrypting password
     * @param password
     * returns salt and encrypted password
     */
    public function hashSSHA($password) {

        $salt = sha1(rand());
        $salt = substr($salt, 0, 10);
        $encrypted = base64_encode(sha1($password . $salt, true) . $salt);
        $hash = array("salt" => $salt, "encrypted" => $encrypted);
        return $hash;
    }

    /**
     * Decrypting password
     * @param salt, password
     * returns hash string
     */
    public function checkhashSSHA($salt, $password) {

        $hash = base64_encode(sha1($password . $salt, true) . $salt);

        return $hash;
    }
}

?>

DB_Connect.php (Web service)


<?php
class DB_Connect {

    // constructor
    function __construct() {

    }

    // destructor
    function __destruct() {
        // $this->close();
    }

    // Connecting to database
    public function connect() {
        /**
         * Database config variables
         */
         define("DB_HOST", "localhost");
         define("DB_USER", "my_db_user");
         define("DB_PASSWORD", "my_db_pass");
         define("DB_DATABASE", "my_db_name");

        // connecting to mysql
        $con = mysql_connect(DB_HOST, DB_USER, DB_PASSWORD);
        // selecting database
        mysql_select_db(DB_DATABASE);

        // return database handler
        return $con;
    }

    // Closing database connection
    public function close() {
        mysql_close();
    }

}
?>

This is all for web service. Now you can go to Android app source codes. In Android:

JSONParser.java (Android)


package com.myapp.library;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

public class JSONParser {

static InputStream is = null;
static JSONObject jObj = null;
static String json = "";

// constructor
public JSONParser() {

}

public JSONObject getJSONFromUrl(String url, List params) {

// Making HTTP request
try {
   // defaultHttpClient
   DefaultHttpClient httpClient = new DefaultHttpClient();
   HttpPost httpPost = new HttpPost(url);
   httpPost.setEntity(new UrlEncodedFormEntity(params));

   HttpResponse httpResponse = httpClient.execute(httpPost);
   HttpEntity httpEntity = httpResponse.getEntity();
   is = httpEntity.getContent();

} catch (UnsupportedEncodingException e) {
   e.printStackTrace();
} catch (ClientProtocolException e) {
   e.printStackTrace();
} catch (IOException e) {
   e.printStackTrace();
}

try {
   BufferedReader reader = new BufferedReader(new InputStreamReader(
     is, "iso-8859-1"), 8);
   StringBuilder sb = new StringBuilder();
   String line = null;
   while ((line = reader.readLine()) != null) {
    sb.append(line + "\n");
   }
   is.close();
   json = sb.toString();
   Log.e("JSON", json);
} catch (Exception e) {
   Log.e("Buffer Error", "Error converting result " + e.toString());
}

// try parse the string to a JSON object
try {
   jObj = new JSONObject(json);
} catch (JSONException e) {
   Log.e("JSON Parser", "Error parsing data " + e.toString());
}

// return JSON String
return jObj;

}
}

UserFunctions.java (Android)

package com.myapp.library;

import java.util.ArrayList;
import java.util.List;

import org.apache.http.NameValuePair;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONObject;

import android.content.Context;

public class UserFunctions {

private JSONParser jsonParser;

private static String loginURL = "http://mywebserviceurl.com/android_login_api/";
private static String registerURL = "http://mywebserviceurl.com/android_login_api/";

private static String login_tag = "login";
private static String register_tag = "register";

// constructor
public UserFunctions(){
jsonParser = new JSONParser();
}

/**
* function make Login Request
* @param email
* @param password
* */
public JSONObject loginUser(String email, String password){
// Building Parameters
List params = new ArrayList();
params.add(new BasicNameValuePair("tag", login_tag));
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));
JSONObject json = jsonParser.getJSONFromUrl(loginURL, params);
// return json
// Log.e("JSON", json.toString());
return json;
}

/**
* function make Login Request
* @param name
* @param email
* @param password
* */
public JSONObject registerUser(String name, String email, String password){
// Building Parameters
List params = new ArrayList();
params.add(new BasicNameValuePair("tag", register_tag));
params.add(new BasicNameValuePair("name", name));
params.add(new BasicNameValuePair("email", email));
params.add(new BasicNameValuePair("password", password));

// getting JSON Object
JSONObject json = jsonParser.getJSONFromUrl(registerURL, params);
// return json
return json;
}

/**
* Function get Login status
* */
public boolean isUserLoggedIn(Context context){
DatabaseHandler db = new DatabaseHandler(context);
int count = db.getRowCount();
if(count > 0){
   // user logged in
   return true;
}
return false;
}

/**
* Function to logout user
* Reset Database
* */
public boolean logoutUser(Context context){
DatabaseHandler db = new DatabaseHandler(context);
db.resetTables();
return true;
}

}

In your application, you can use this UserFunctions.java like that:

import com.myapp.library.UserFunctions;

Lets say our response JSON of webservice will be like that:

{ "success": 1,
"user": {
     "name":"Seval",
     "email":"hello@hotmail.com"
   }
}

You can call parse the results in a function, for example "loginUser":

JSONObject json = userFunction.loginUser(email, password);

// check for login response
String res = json.getString("success");
if(Integer.parseInt(res) == 1){
   JSONObject json_user = json.getJSONObject("user");
   String name = json_user.getString("name");
   String email = json_user.getString("email");
}

Mysql Query

2015-04-09T03:47:00.001-07:00

How to get second-highest salary employees in a table

- Method 1

select max(salary) from Employees

where salary < (select max(salary) from Employees)

- Method 2

select MAX(salary) from Employees

where salary not in(select MAX(salary) from Employees)

- Method 3

select MAX(salary) from Employees

where salary != (select MAX(salary) from Employees )

-Method 4

SELECT salary from Employee ORDER BY salary DESC LIMIT 1, 1;

How to calculate Second Largest Salary

SELECT * FROM `book_book`as e WHERE 2=(select count(book_id) from book_book where e.book_id<=book_id)

Display Database Engines

  SHOW ENGINES

Display Database

  SHOW DATABASES

Query to select book categories which start with Non-alphabets

[SQL] SELECT * FROM `book_bookcategories` WHERE `book_category_name` NOT REGEXP '^[a-z]' ORDER BY `book_bookcategories`.`book_category_name` DESC [/SQL]

Query to select DUPLICATE categories with duplicate count

SELECT COUNT( * ) , `book_category_name` FROM `book_bookcategories`

GROUP BY book_category_name HAVING COUNT( * ) >1 LIMIT 0 , 30

Query to remove duplicate elements.

CREATE TABLE mytable as(SELECT DISTINCT (`book_category_name`) FROM book_bookcategories)

Perform operations on date

SELECT * FROM `seller_feedback` WHERE `feedback_date`>(SELECT (CURDATE()- INTERVAL 6 MONTH))

update `subcategory` set sub_name = if(sub_name='black','white','black') where sub_name='black'

 or sub_name='white'

update subcategory set sub_name = case sub_name when 'white' then 'black' when 'black' then 'white'

end where sub_name in('white','black')

update subcategory set sub_name = case sub_name when 'white' then 'black' 'white' end where sub_name

in('white','black')

Differences between SESSION and COOKIE

COOKIE
A cookie is a text-only string that takes a place in the memory of user’s browser. If the lifetime of the cookie is set to be longer than the time user spends at that site, then this string is saved to file for future reference. User could be disabled the cookie in their browser setting.

SESSION
Session values are store in server side not in user’s machine. A session is available as long as the browser is opened. User couldn’t be disabled the session. We could store not only strings but also objects in session.

Cookies
Cookies are client-side files that contain user information

In php $_COOKIE super global variable is used to manage cookie.
You don't need to start Cookie as It is stored in your local machine.
Official MAX Cookie size is 4KB
 
There is no function named unsetcookie() ,
Cookie ends depends on the life time you set for it.
Print cookies print_r($_cookies);
you can create a cookie by using setcookie() function:

Super Global variables are an associative array, they are predefined by PHP.They are super global because they are available in all scopes on script.
There are several types of Super Global Variables :-

$_GET

$_GET is an associative array which accept parameter from URL as query string.

What is query string ?
Query string is KEY=>VALUE pairs of URL after Question Mark(?) Symbol.
We can say complete string after Question Mark Symbol is "Query String". The question mark is used as a separator and is not part of the query string.

How can we get Query String in our PHP page ?
With the help of $_GET super global variable.
For example if URL is :-
http://localhost/get_test.php?name=rasmus&age=35&lang=php
Then in above URL Query String is
" name=rasmus&age=35&lang=php "

key and value pairs are separated with = symbol.
Ex: "name=rasmus"
here "name is key" and "rasmus is value".

Group of those key and value pairs are separated with & sybmol.

<?php

  echo "<pre>";

  print_r($_GET);

?>

<form name="test_post" action="" >

<input type="email" required name="email" placeholder="type email here" ><br>

 <input type="password" required name="pass" placeholder="type password here"><br>

<input type="submit" >

</form>

$_POST

$_POST is an associative array that accept parameters as KEY=>VALUE pairs from submission of HTML in $_POST super global variable as key=>value pairs

In $_POST

key is name of element in input form
value is value of that element in input form

for example :

<?php

echo "<pre>";

print_r($_POST);

</form>

$_REQUEST

$_REQUEST is an associative array which we can use in place of $_GET or $_POST.

It means $_REQUEST is parent of $_GET and $_POST.

$_REQUEST

$_GET
$_POST

instead of using $_GET and $_POST we can use $_REQUEST.

If $_REQUEST can perform working of $_GET and $_POST both then why we use $_GET and $_POST separately.

It is bad programming practice if we use always $_REQUEST instead of $_GET and $_POST because it leads into confusion of another developer that from where variable value is coming.

$_GET is dedicated to accept parameters from URL

$_POST is dedicated to accept parameters through HTML

$_FILES

$_FILES is responsible to accept binary/octet stream which we want to upload with browse button.

$_SESSION

$_SESSION is super global variable which is used to maintain session from Local machine to Server.

$_COOKIE

$_COOKIE is super global variable which is used to save/get user data on same machine in browser cookies.

$_SERVER

$_SERVER is an associative array which is used to know server information.

$_ENV

$_ENV is superglobal variable which is used to manage environment variable.

What is the basic difference between INNODB and MYISAM?

#	INNODB	MYISAM
1	INNODB is default storage engine on Windows	MYISAM is default storage engine on Linux
2	INNODB support COMMIT, ROLLBACK, and crash-recovery capabilities to protect user data because it support ACID property.	MYISAM didn't support.
3	INNODB support ROW-LEVEL Locking(multiprocessing on single table).	MYISAM support TABLE-LEVEL locking.
4	UPDATE and DELETE query will execute faster because it support ROW-LEVEL lock.	SELECT query will execute faster because it support TABLE level lock.
5	INNODB support FOREIGN-KEY referential-integrity constraints.	MYISAM didn't support.
6	INNODB didn't support Full-Text searching.	MYISAM support Full-Text searching.
7	InnoDB has been designed for maximum performance when processing large data volumes,because Row data stored in Primary Key order	No ordering in storage of data
8	Each INNODB table is stored on disk in single file(.FRM)	Each MyISAM table is stored on disk in three files(.MYD, .MYI, .FRM) .FRM Table Format .MYD MY Data .MYI MY Index

SQL SELECT Query

SQL SELECT Statement

The SELECT Query the basic query is used to retrieve the selected data from database. This is very powerful and largely used command. The result of the select query is stored in result table which is also called as result-set

It’s part of the data manipulation language that is responsible for query the data from the database.
SQL SELECT statement syntax

It is the most frequently used SQL command and has the following general syntax

SELECT column_name(s) FROM table_name

SELECT * FROM table_name

[SELECT column_name(s)] – The result set retrieve all entered columns data. It may contain multiple columns. If pass ‘*’ then it results all columns from selected table.
[FROM table_name] – This is a table name from which result set is retrieved.

Examples:
Let’s see upon executing following query on Employee table resulting following list:

SELECT * FROM Employee

Following is the result after executing the above SQL query:

Employee_Id	Full_Name	Gender	Date_Of_Birth	Phone
1	Tanya Smith	Female	1982-09-30	9123456789
2	Janet Tampi	Female	1980-07-10	9876543210
3	Nilsen Phil	Male	NULL	9112233445
4	Nilsen Jones	Male	1983-09-17	9988776655
5	Pettersen Willams	Male	1980-07-12	9944552299

Note: In SQL all queries are case insensitive, so we can use command SELECT or select.

In above query we have seen how to get all the rows and columns from the Employee table.

Using the SELECT keyword allows you to select all columns or specific column(s). The ‘*’ is used to select all columns in the result set & if you want to any specific column(s) in the result set then you can specify comma separated column name list after the SELECT keyword like the one shown below:

SELECT Full_name, Date_Of_Birth, Phone FROM Employee

Following is the result after executing the above SQL query:

Full_Name	Date_Of_Birth	Phone
Tanya Smith	1982-09-30	9123456789
Janet Tampi	1980-07-10	9876543210
Nilsen Phil	NULL	9112233445
Nilsen Jones	1983-09-17	9988776655
Pettersen Willams	1980-07-12	9944552299

SQL Concat Function:

SQL query also supports the functions to join the column data & display in one column. The Concat () function is used in the SELECT query to join the multiple column data.

If you are looking for Employee Name with Gender in the format of [Full_Name, (Gender)] then Concat () function will help you to retrieve the required data in the above format using following query:

SELECT Concat(Full_Name, '(', Gender, ')'), Phone FROM Employee

In this query:

Concat () SQL function is used join the two columns values together.
The line “Concat(Full_Name, ‘(‘, Gender, ‘)’)” sentence is used to join the Full_Name & Gender column data. Use of opening & closing brackets is in Concat function with list of column names.

Following is the result after executing the above SQL query:

	Phone
Tanya Smith (Female)	9123456789
Janet Tampi (Female)	9876543210
Nilsen Phil (Male)	9112233445
Nilsen Jones (Male)	9988776655
Pettersen Willams (Male)	9944552299

SQL Alias:

When we use the any function in the SQL query and execute the query then in the result set name of the column is showing weird. Here while using any function in the query we can use Alias name so that in the result set name of the column is appears as the Alias name what you entered.

SELECT Concat(Full_Name, '(', Gender, ')') [AS] Name(M/F), Phone FROM Employee

Following is the result after executing the above SQL query:

Name (M/F)	Phone
Tanya Smith (Female)	9123456789
Janet Tampi (Female)	9876543210
Nilsen Phil (Male)	9112233445
Nilsen Jones (Male)	9988776655
Pettersen Willams (Male)	9944552299

Such as Concat() function SQL support lots of function, Here you can get list of most popular function used regularly in testing:

SQL Aggregate Functions:

SQL sum()
SQL max()
SQL min()
SQL avg()
SQL first()
SQL last()
SQL count()

SQL Scalar Functions:

SQL format()
SQL lcase()
SQL ucase()
SQL len()
SQL mid()
SQL now()
SQL round()

SQL Where Clause

The SQL WHERE clause is powerful & one of the most commonly used clause use in day to day life. Basically It allows you to filter out the result set and your get limited data based on condition. The WHERE clause can be used alongwith the SQL SELECT statement, SQL INSERT statement,, SQL UPDATE statement, or SQL DELETE statement.

SQL WHERE clause syntax

It is the most frequently used SQL command and following is the general syntax of SELECT command with WHERE clause to fetch data from table:

SELECT column_name(s)

FROM table_name

WHERE column_name operator value

[SELECT column_name(s)] – The result set retrieve all entered columns data. It may contain multiple columns. If pass ‘*’ then it results all columns from selected table.
[FROM table_name] – This is a table name from which result set is retrieved.
[WHERE] – This Clause used to filter out the result data set based on “condition”. You can specify any condition using WHERE clause. It supports AND or OR operators to specify more than one condition in single query.

The WHERE clause works similar to IF condition used in the coding language. This clause is used to compare given value with the field value available in MySQl table. If given value from outside is equal to the available field value in MySQL table then it returns that row.

Let’s take example A=100 and B=200 and see how operators works with this example:

Operator	Description	Example
=	This operator checks the values of both fields are same.	[A = B] is False
!=	This operator checks the values of both fields are not same.	[A != B] is True.
<	This checks the value of left operand is less than the value of right operand. If this condition satisfies then result is True.	[A < B] is True.
>	This checks the value of left operand is greater than the value of right operand. If this condition satisfies then result is True.	[A > B] is not True.
<=	This checks the value of left operand is less than equal to the value of right operand. If this condition satisfies then result is True.	[A <= B] is True.
>=	This checks the value of left operand is greater than equal to the value of right operand. If this condition satisfies then result is True.	[A >= B] is not True.

Examples:
Let’s see upon executing following query on Employee table resulting following list:

SELECT * FROM Employee

Following is the result after executing the above SQL query:

Employee_Id	Full_Name	Gender	City	Phone
1	Tanya Smith	Female	Stavanger	9123456789
2	Janet Tampi	Female	Chicago	9876543210
3	Nilsen Phil	Male	NULL	9112233445
4	Nilsen Jones	Male	Atlantic	9988776655
5	Peter Willams	Male	Sandnes	9944552299

Let’s now look at a practical example.

SELECT * FROM Employee

WHERE Employee_Id = 2

Following is the filtered result after executing the above SQL query:

Employee_Id	Full_Name	Gender	City	Phone
2	Janet Tampi	Female	Chicago	9876543210

AND logical operator:

SELECT * FROM Employee

WHERE Full_Name = ‘Nilsen Jones’

AND Gender = 'Male'

Following is the filtered result after executing the above SQL query using AND Logical Operator:

Employee_Id	Full_Name	Gender	City	Phone
4	Nilsen Jones	Male	Atlantic	9988776655

OR logical operator:

SELECT * FROM Employee

WHERE Employee_Id = 1 OR Employee_Id = 2

Following is the filtered result after executing the above SQL query using OR Logical Operator:

Employee_Id	Full_Name	Gender	City	Phone
1	Tanya Smith	Female	Stavanger	9123456789
2	Janet Tampi	Female	Chicago	9876543210

IN logical operator:

SELECT * FROM Employee

WHERE City IN (‘Chicago’, ‘Atlantic’)

Following is the filtered result after executing the above SQL query using IN Logical Operator:

Employee_Id	Full_Name	Gender	City	Phone
2	Janet Tampi	Female	Chicago	9876543210
4	Nilsen Jones	Male	Atlantic	9988776655

NOT IN logical operator:

SELECT * FROM Employee

WHERE City <strong>NOT</strong> IN (‘Chicago’, ‘Atlantic’)

Following is the filtered result after executing the above SQL query using NOT IN Logical Operator:

Employee_Id	Full_Name	Gender	City	Phone
1	Tanya Smith	Female	Stavanger	9123456789
3	Nilsen Phil	Male	NULL	9112233445
5	Peter Willams	Male	Sandnes	9944552299

BETWEEN logical operator:

SELECT * FROM Employee

WHERE Employee_Id BETWEEN 2 AND 4

Following is the filtered result after executing the above SQL query using

Employee_Id	Full_Name	Gender	City	Phone
2	Janet Tampi	Female	Chicago	9876543210
3	Nilsen Phil	Male	NULL	9112233445
4	Nilsen Jones	Male	Atlantic	9988776655

LIKE logical operator:

Ending Wildcard:

SELECT * FROM Employee

WHERE Full_Name LIKE 'N%'

Following is the filtered result after executing the above SQL query using LIKE Logical Operator with Ending Wildcard:

Employee_Id	Full_Name	Gender	City	Phone
3	Nilsen Phil	Male	NULL	9112233445
4	Nilsen Jones	Male	Atlantic	9988776655

Leading Wildcard:

SELECT * FROM Employee

WHERE Full_Name LIKE '%s'

Following is the filtered result after executing the above SQL query using LIKE Logical Operator with Leading Wildcard:

Employee_Id	Full_Name	Gender	City	Phone
4	Nilsen Jones	Male	Atlantic	9988776655
5	Peter Willams	Male	Sandnes	9944552299

Multiple Wildcards:

Find any record which has anywhere, the letter ‘a’

SELECT * FROM Employee

WHERE Full_Name LIKE '%a%'

Following is the filtered result after executing the above SQL query using LIKE Logical Operator with Middle Wildcard:

Employee_Id	Full_Name	Gender	City	Phone
1	Tanya Smith	Female	Stavanger	9123456789
2	Janet Tampi	Female	Chicago	9876543210
5	Peter Willams	Male	Sandnes	9944552299

Single Character Wildcard:

Find the record which has Name started with ‘J’ and has ‘a’ character anywhere in record.

SELECT * FROM Employee

WHERE Full_Name LIKE 'J%a%'

Following is the filtered result after executing the above SQL query using LIKE Logical Operator with Single Character Wildcard:

Employee_Id	Full_Name	Gender	City	Phone
2	Janet Tampi	Female	Chicago	9876543210

Summary:

The SQL WHERE clause is used to filter the number of rows in result set based on condition.
The WHERE clause can be used with a SELECT, UPDATE or DELETE query.
In the WHERE clause allows you to write the condition using logical operators like AND, OR, LIKE, BETWEEN, IN, NOT IN etc.
Using AND operator means the all condition should satisfies.
Using OR operator means the any condition satisfies.
Using IN keyword is basically used to choose rows matching a list of values.

SQL Order by clause

Order by clause:

To sort the result set we can use Order by clause in either ascending or descending order. This clause is used with conjection of SELECT statement.

What are DESC and ASC Keywords?

DESC is used to the query to sort result by descending	ASC is used to the query to sort result by ascending
Query result is sorted from Bottom to Top.	Query result is sorted from Top to Bottom.
For Date types the latest dates are resulted at the top of the result list.	For Date types the old dates are resulted at the top of the result list.
For Numeric data types the Largest number are resulted at the top of the result list.	For Numeric data types the lowest number are resulted at the top of the result list.
For String data types the result list is sorted with the letter from Z to A.	For String data types the result list is sorted with the letter from A to Z.

The DESC and ASC keywords are used with the combination of Select statement & the ORDER BY clause.

Let’s see how these both keywords are use in the basic query statement:

ASC/DESC basic syntax:

SELECT column_name(s)

FROM table_name

WHERE condition

ORDER BY column_name(s) ASC|DESC

So here we see what is use of each objects:

[SELECT column_name(s)] – The result set retrieve all entered columns data. It may contain multiple columns. If pass ‘*’ then it results all columns from selected table.
[FROM table_name] – This is a table name from which result set is retrieved.
[WHERE condition] – It is used to restrict result set based on the given condition. It is optional Condition.
ORDER BY –The ORDER BY keyword is used to sort the result-set by a specified column. If we do not pass the ASC or DESC then default ASC is considered.

Examples:
Let’s see upon executing following query on Employee table resulting following list:

SELECT * FROM Employee

Following is the result upon executing the above SQL query:

Employee_Id	Full_Name	Gender	Date_Of_Birth	Phone
1	Tanya Smith	Female	1982-09-30	9123456789
2	Janet Tampi	Female	1980-07-10	9876543210
3	Nilsen Phil	Male	NULL	9112233445
4	Nilsen Jones	Male	1983-09-17	9988776655
5	Peter Willams	Male	1980-07-12	9944552299

If company wants the list of employee details list with the elder to younger as Birthday. So you can get a list by executing query on database using Order by keyword with DESC as below.

SELECT * FROM Employee ORDER BY Date_Of_Birth DESC

Following is the result upon executing the above SQL query:

Employee_Id	Full_Name	Gender	Date_Of_Birth	Phone
4	Nilsen Jones	Male	1983-09-17	9988776655
1	Tanya Smith	Female	1982-09-30	9123456789
5	Peter Willams	Male	1980-07-12	9944552299
2	Janet Tampi	Female	1980-07-10	9876543210
3	Nilsen Phil	Male	NULL	9112233445

Note: In the sorting NULL values means consider as no values i.e. not zero or empty string. In this example we also see how the NULL results are sorted.

We can use same query with ascending order by using following query:

SELECT * FROM Employee

ORDER BY Date_Of_Birth ASC

SELECT * FROM Employee

ORDER BY Date_Of_Birth

Following is the result upon executing the above SQL query:

Employee_Id	Full_Name	Gender	Date_Of_Birth	Phone
3	Nilsen Phil	Male	NULL	9112233445
2	Janet Tampi	Female	1980-07-10	9876543210
5	Peter Willams	Male	1980-07-12	9944552299
1	Tanya Smith	Female	1982-09-30	9123456789
4	Nilsen Jones	Male	1983-09-17	9988776655

If we sort the result using String then, the query result set are sorted from those starting with the letter Z going down to the letter A.

SELECT * FROM Employee

ORDER BY Full_Name ASC

Following is the result upon executing the above SQL query:

Employee_Id	Full_Name	Gender	Date_Of_Birth	Phone
2	Janet Tampi	Female	1980-07-10	9876543210
4	Nilsen Jones	Male	1983-09-17	9988776655
3	Nilsen Phil	Male	NULL	9112233445
5	Peter Willams	Male	1980-07-12	9944552299
1	Tanya Smith	Female	1982-09-30	9123456789

We can use the Sorting of two column using Single query. In this example we are sorting first column with ascending & second column with descending order.

Conclusion on ORDER BY, DESC and ASC:

You can sort the result ser either in ascending or descending order using ASC or DESC keywords.
To sort the result in ascending order the “ASC” keyword is used.
If we do not pass the keyword with the ORDER BY then default keyword “ASC” is used to sort the search result.
To sort the result in descending order the “DESC” keyword is used.
Using Order by clause conjunction with SELECT both DESC and ASC works. To limit the search result we can use WHERE clause.

SQL INSERT INTO

What is SQL INSERT INTO?

The primary objective of database systems is basically used to store the data in to database & recall the same state of data from database whenever required. The data is handled by the application which is executed over the top of database. So basically the INSERT INTO command is used to store the data into database. The SQL INSERT INTO command is always add a new record into the table.

SQL INSERT INTO Syntax

Let’s see the basic syntax of Insert into command:

INSERT INTO Table_Name

VALUES (Value1, Value2, Value3,...);

You can also use the following command to insert data in specific rows which you have want to specify:

INSERT INTO Table_Name (Column1, Column2, Column3,...)

VALUES (Value1, Value2, Value3,...);

INSERT INTO Table_Name – The INSERT INTO command is used to tell database to insert new specified values in the Table_Name which you have specified.
(Column1, Column2, Column3,…) – These are the name of the columns for which you have to add the new record in the table.
VALUES (Value1, Value2, Value3,…) – These are the actual data to be added in the new row.

Before inserting new records, the main important thing to keep in mind is the Data Types. There are different data types & when adding a new row, you should ensure the datatype of the value and the column matches. For all string data types values should be enclose in the single quotes & all numberic data types values should be enter directly without enclosing into single quotes.

Demo Database:

In this tutorial we will use the demo well-known Northwind sample database.

Employee_Id	Full_Name	Address_Line_1	City	Phone
1	Tanya Smith	Rua do Mercado	Stavanger	9123456789
2	Janet Tampi	Keskuskatu Road	Chicago	9876543210
3	Nilsen Phil	Skagen, 21 Floor	NULL	9112233445
4	Nilsen Jones	305 – 14th Ave. S. Suite 3B	Atlantic	9988776655
5	Peter Willams	Torikatu 38	Sandnes	9944552299

Let’s take a example of Employee table & insert few entries in different fashion using sql server INSERT INTO command. We will add new Employee record in the Employee table with including the column names.

Insert into  Employee

(Full_Name, Address_Line_1, City, Phone)

Values (‘Wilman Kala’, ‘305 - 14th Ave. S. Suite 3B’, ‘Seattle’, 9988665522);

Conclusion:

The SQL INSERT INTO statement is used to insert new records in a table.
Single quotes should be excluded while inserting the numeric values.
The string and date values should be enclosed in single quotes.
The INSERT command can also be used to insert data into specified columns only.

SQL UPDATE and DELETE

What is the UPDATE keyword?

The UPDATE command is used to modify the records in the table. Upon executing this command the record values are modified based on values passed in the query. Along with WHERE clause you can update the specific records from the table.

SQL UPDATE Syntax:
Let’s see the basic syntax of DELETE command:

UPDATE Table_Name

SET ‘Column_Name’ = ‘New_value’

[WHERE CONDITION];

So here we see what use of each object:

[UPDATE Table_Name] – This command is used to tell database to modify the records from specified Table_Name.
[SET ‘Column_Name’ = ‘New_value’] – ‘Column_Name’ are the name the column for which you have to modify the value & ‘New_value’ are the actual value which you have to set. While setting up the new values you have to enter the new values based on the column’s data type, means if column value is Full_Name with data type varchar then you have to specify the values in the single quotes. Similarly for date data type you have to enter date values single quotes. Numeric values you have to specify the values without quotes.
[WHERE CONDITION] – This Clause used to filter out the result data set based on “condition”. You can specify any condition using WHERE clause.

Let’s go ahead & learn update query with practical example. In the Employee table each record have Phone & one Employee want to change the phone number in the employee record & second employee want to update the Full name. So let’s see how to update the Phone number using UPDATE query.

SELECT * FROM Employee WHERE Employee_Id IN (1,2);

Employee_Id	Full_Name	Gender	Date_Of_Birth	Phone
1	Tanya Smith	Female	1982-09-30	9123456789
2	Janet Tampi	Female	1980-07-10	9876543210
3	Nilsen Phil	Male	NULL	9112233445
4	Nilsen Jones	Male	1983-09-17	9988776655
5	Pettersen Willams	Male	1980-07-12	9944552299
6	Angels David	Male	1981-02-10	9955566611

The Employee “Tanya Smith” wants to change phone number from “9123456789” to “9198657777” & “Janet Tampi” want to update the Full name to “Janet Tampi – Simson” & Date of birth to “1980-07-10”, so you can use following update queries to modify the records.

UPDATE Employee

SET Phone = ‘9198657777’

WHERE Employee_Id  = 1;

UPDATE Employee

SET Full_Name = ‘Janet Tampi - Simson’, Date_Of_Birth = ‘1980-08-10’

WHERE Employee_Id  = 2;

What is SQL DELETE keyword?

As it name suggest that the DELELE keyword is used to delete the record(s) from database when they are no longer be used. Using DELETE keyword you can delete single or multiple records from the database. So this command is used more powerfully with WHERE keyword while removing the unnecessary records from the database.

Upon executing this command the deleted data cannot be recovered, so prior executing this command you should make sure with where condition in the query is correct. To be on safer side, take the backups of database or tables from where you are executing the delete query, so it will help you to compare the records after executing the query.

SQL DELETE Syntax
Let’s see the basic syntax of DELETE command:

DELETE from Table_Name

[WHERE CONDITION];

In above case we have specified WHERE condition, so the records will be deleted from table based on the criteria you specified.
You can also use the following command to delete all the data from table, so only difference is don’t specifiy the WHERE condition:

DELETE from Table_Name;

So here we see what use of each object:

[DELETE from Table_Name] – This command is used to tell database to delete the records from specified Table_Name.

[WHERE CONDITION] – This Clause used to filter out the result data set based on “condition”. You can specify any condition using WHERE clause.

DELETE FROM Employee WHERE Employee_Id = 4;

Summary

The UPDATE command is modify the existing records in the database.
To modify the limited records in the database you can use WHERE clause is used along with UPDATE command.
The DELETE command is use to delete the records in the database which are no longer required in database.
Once you delete the records then same records cannot be recovered again, so make sure you have taken up backup prior to executing DELETE command.
To delete the limited records in the database you can use WHERE clause is used along with DELETE command.

SQL Sub-Queries

What are Sub queries?

SQL Sub queries are the queries which are embedded inside another query. The embedded queries are called as INNER query & container query is called as OUTER query.

The subqueries are the queries which are executed inside of another query. The result SQL query is totally depends on the result of sub query. First the INNER query gets executed & the result of INNER query is passed as input to the outer query.

SQL Sub-Query Syntax:

Let’s look at the basic syntax of the SQL Sub query command:

Three types of sub queries are supported in SQL are – Scalar, Row and Table sub queries.

The Scalar subquery result returns only a single row and single column.
The Row subquery result returns only a single row with single/multiple column(s).
The Table subquery result returns can be return single/multiple row(s) or column(s).

In the Sub query you may use the different operators to filter out the result like [=, >, =, <=, !=, ]. These Sub queries can be used conjunction with INSERT, UPDATE and DELETE queries.

Suppose you want to find the name of the department in which employee_id = 100 is currently working on.

Let’s see how this sub query is constructed & executed inside of another query:

SELECT department_name FROM department

WHERE department_id =

(SELECT department_id FROM employee WHERE employee_id = 100);

Following is the result upon executing the above SQL Sub query:

So let’s discuss how the result of above query is calculated:

In above Row Sub-Queries, the result of INNER query can is returned only one value.

Let’s take a look at the other Sub query type who returns can be return single/multiple row(s) or column(s) i.e. Table sub-query:

Suppose you want get list of employee’s Name and Phone number who’s working in other than Quality department & date of birth is not registered in Employee tracking system.

SELECT Full_name,Phone FROM Employee

WHERE date_of_birth is NULL and department_id IN

(SELECT department_id FROM department WHERE department_name  <> ‘Quality’)

Following is the result upon executing the above SQL Sub query:

So let’s discuss how the result of above query is calculated:

You can use multiple INNER queries inside INNER queries, the SQL supports INNER queries up to 32 levels.

In above examples we have seen INNER queries up to two levels; here we are seeing three level INNER query:

In the company higher managements wants to announce the awards to highest paying employee member, so here is the query to get the name of the highest paying employee:

Select Full_name From employee WHERE Employee_id =

(SELECT Employee_id FROM payments WHERE salary =

(SELECT MAX(salary) FROM payments))

Sub-Queries Vs Joins!

The Subqueries are simpler to write & easy to understand. As a result, Sub queries are more frequently used in the beginner’s level. The Joins are complicated but more powerful than Sub queries.

Majorly sub queries run independently and result of the sub query used in the outer query (other than correlated sub query) and in case of JOIN’s, a query only give the result when the joining condition gets satisfied.

In JOIN both the tables should have a common column name but in sub query without having a column name we can execute the query.

If we think in terms of the performance prospective, then the Joins are faster than the Sub queries. Using Joins, it approximately boosts the performance of query by 500 times as compare to Sub queries. So Joins are more popular than the Sub queries & most of the SQL experts are preferred to use Joins instead of SubQueries.

Conclusion on SQL Sub-Queries:

Sub queries contain two parts, one is INNER query & other is OUTER query. The result of INNER query is passed to OUTER query as input.
Sub queries are simple & easy to understand. It can be easily broken down into logical steps, so it offers more flexibility.
The Sub queries are used in conjunction with SELECT, INSERT, UPDATE & DELETE commands.
In this article we have learnt about three types of SQL supb queries: scalar, row and table sub queries.
In SQL server, The Nested query can be used up to 32 levels.
As compare with Joins, the performance of Sub query is low. Joins are 500 times faster than Sub queries.

SQL JOIN's

What is SQL JOIN’s?

In the expert level JOIN’S are more common SQL commands used in day to day life. JOIN’s are used to retrieving the records from multiple tables. SQL allows you to take JOIN’s on multiple tables from same database as well as different databases from same server.

Basically the tables are interrelated with each other using Primary & foreign key. So these keys are used in the JOIN’s to interlink two tables.

Why should we use JOIN’s?

Many times you are thinking “Why use SQL JOIN’s” as same task can be done using different queries. In the database queries are executed one by one & result of successive query can be use for next query. If we use the JOIN’s queries then instead of processing multiple queries SQL server process only single query which reduce the SQL server overhead. The main advantage of SQL JOIN’s is the improved performance. Also using multiple queries lead more data transfer from SQL server to application which reduces the performance.

Types of SQL JOINs:

Before we start learning SQL JOIN’s, we will see the list of different types of SQL JOINs:

INNER JOIN: The INNER JOIN keyword selects all rows from both tables as long as there is a match between the columns in both tables (Table1 and Table2).
LEFT JOIN: The LEFT JOIN keyword returns all rows from the left table (Table1), with the matching rows in the right table (Table2). The result is NULL in the right side when there is no match.
RIGHT JOIN: The RIGHT JOIN keyword returns all rows from the right table (Table2), with the matching rows in the left table (Table1). The result is NULL in the left side when there is no match.

FULL JOIN: The FULL OUTER JOIN keyword returns all rows from the left table (Table1) and from the right table (Table2). The FULL OUTER JOIN keyword combines the result of both LEFT and RIGHT joins.

Let’s go ahead & learn different types of JOIN queries with practical example. Following are the three tables, Customers Product & Order.

SQL INNER JOIN Keyword:

The INNER JOIN is selects all rows from both tables as sql query match the specified condition.

SQL INNER JOIN Syntax:

SELECT column_name(s)

FROM Table1

JOIN Table2

ON Table1.column_name=Table2.column_name;

SELECT column_name(s)

FROM Table1

INNER JOIN Table2

ON Table1.column_name=Table2.column_name;

In the query you can use JOIN or INNER JOIN, both are same

INNER JOIN Query Example:

Suppose, the dealer want the list of order details like Product name, Unit Price, Quantity & Price. So in this case you can use INNER JOIN to get the records from both Product & Order tables. The ProductId is common in both tables. So in the INNER JOIN condition is added on ProductId & only matching records from Product & Order tables are returned.

SELECT T2.OrderID, T1.ProductID, T1.Name, T1.UnitPrice, T2.Quantity, T2.Price

FROM Product AS T1

INNER JOIN Order AS T2 ON T1.ProductID = T2.ProductID

ORDER BY T2.OrderID

Following is the result upon executing the above SQL INNER JOIN query:

SQL LEFT JOIN Keyword:

LEFT JOIN returns all records/rows from left table and from right table returns only matched records. Where no matches have been found in the table on the right, NULL is returned.

SQL LEFT JOIN Syntax:

SELECT column_name(s)

FROM Table1

LEFT JOIN Table2

ON Table1.column_name=Table2.column_name;

SELECT column_name(s)

FROM Table1

LEFT OUTER JOIN Table2

ON Table1.column_name=Table2.column_name;

LEFT JOIN query Example:

SELECT T2.OrderID AS OrderID, T1.ProductID, T1.Name, T1.UnitPrice, T2.Quantity AS Quantity, T2.Price AS Price

FROM Product AS T1

LEFT OUTER JOIN Order AS T2 ON T1.ProductID = T2.ProductID

ORDER BY T1.ProductID

Following is the result upon executing the above SQL LEFT OUTER JOIN query. You can see the all records from the Product table & NULL values are displayed for all records where no matching records found in Order table.

SQL RIGHT JOIN Keyword:

RIGHT JOIN is exact opposite to LEFT JOIN, it returns all records/rows from right table and from left table returns only matched records. Where no matches have been found in the table on the left, NULL is returned.

SELECT column_name(s)

FROM Table1

RIGHT JOIN Table2

ON Table1.column_name=Table2.column_name;

SELECT column_name(s)

FROM Table1

RIGHT OUTER JOIN Table2

ON Table1.column_name=Table2.column_name;

RIGHT JOIN query Example:

SELECT T2.OrderID AS OrderID, T1.ProductID, T1.Name, T1.UnitPrice, T2.Quantity AS Quantity, T2.Price AS Price

FROM Product AS T1

RIGHT OUTER JOIN Order AS T2 ON T1.ProductID = T2.ProductID

ORDER BY T1.ProductID

Following is the result upon executing the above SQL RIGHT JOIN query. You can see the all records from the Order table & NULL values are displayed for all records where no matching records found in Product table. But if all records are matched then it will left table then no NULL records are returned in result set.

SQL FULL OUTER JOIN Keyword:

FULL OUTER JOIN combines left outer join and right outer join. This join returns all records/rows from both the tables. If there are no columns matching in the both tables, it returns NULL values.

SQL FULL OUTER JOIN Syntax:

SELECT column_name(s)

FROM Table1

FULL OUTER JOIN Table2

ON Table1.column_name=Table2.column_name;

FULL OUTER JOIN query Example:

Suppose we want to get all Order records against all the Product records, then we can use the FULL OUTER JOIN script shown below to get all records from both tables.

SELECT T2.OrderID AS OrderID, T1.ProductID, T1.Name, T1.UnitPrice, T2.Quantity AS Quantity, T2.Price AS Price

FROM Product AS T1

FULL OUTER JOIN Order AS T2 ON T1.ProductID = T2.ProductID

ORDER BY T1.ProductID

Following is the result upon executing the above SQL FULL OUTER JOIN query:

Conclusion on SQL JOINS:

· JOIN’s are used to combine & get the data from different tables.

· INNER JOIN returns rows when there is a match in both tables.

· LEFT JOIN returns all rows from the left table, even if there are no matches in the right table.

· RIGHT JOIN returns all rows from the right table, even if there are no matches in the left table.

· FULL JOIN returns rows when there is a match in one of the tables.

· The performances of JOIN’s are better than sub queries.

· In the OUTER JOIN’S when no records are returned then NULL values are returned in the result set.

· JOIN queries can be used with the conjunction of SELECT, INSERT, UPDATE, DELETE commands.

· Also we can use different clauses along with JOIN’s like GROUP BY, WHERE, SUB QUERIES, AGGREGATE FUNCTIONS etc.

SQL UNION

What is a SQL UNION?

The SQL UNION operator allows you to combine the result of two or more SQL SELECT queries.

The only requirement to work SQL UNION query is both the SQL SELECT queries must having the same number of columns in the result set & with same data type.

SQL UNION Syntax:

SELECT column_name(s) FROM table1

UNION

SELECT column_name(s) FROM table2;

If we use UNION operator in the query then all unique records are returned in the result set. The duplicate records from the result set are displayed once.

SQL UNION example:

Let take example, we have following two tables called Table1 and Table2:

First we will see how SQL UNION operator is combining the results of the two select statements:

SELECT Column1, Column2 FROM Table1

UNION

SELECT Column1, Column2 FROM Table2;

Following is the result upon executing the above SQL UNION query, the only unique records are returned from both tables.

Note: If we not specify any keyword with UNION operator then by default it take DISTINCT keyword i.e. “UNION DISTINCT”

Now we will see how SQL UNION ALL operator is combining the results of the two select statements:

SELECT Column1, Column2 FROM Table1

UNION ALL

SELECT Column1, Column2 FROM Table2;

Following is the result set upon executing the above SQL UNION ALL query, the result set includes all records including duplicate records from both tables, so the duplicate rows are repeated in the result set.

UNION operator is by default returns the unique records. If you want to get the all rows including duplicate records then you can use “ALL” keyword with UNION.

Difference between SQL JOIN and UNION:

In the JOINS, the columns may be different in the tables but in the UNION the number of column must be same.
In case of UNION result set put rows one after each other i.e. result set puts vertically. But in case of JOIN result set put column one after each other i.e. result set puts horizontally. UNION makes a Cartesian product.
UNION is used for joining 2 result sets and JOIN is used for joining two or more tables, views, table-valued functions.

Conclusion on SQL UNION Queries:

UNION operator is used to combine the result sets of two SELECT statements & combined result set includes all records from both tables.
The number of columns & column data types must be same for using the UNION operator.
The UNION DISTINCT keyword is returns the duplicate records from the result set. In the UNION operator if no any keyword is specified then it acts as DISTINCT keyword.
UNION ALL simply joins 2 result sets including all the rows,does not remove the duplicate records from the result set.

SQL GROUP BY Clause

What is the SQL Group by Clause?

The SQL GROUP BY clause is used to group the result set based on common value present in the result set. The grouping of result set is done after all records are retrieved from tables.
The GROUP BY clause can be used with the conjunction of SELECT query to make a group of rows based on the values of a specific column or expression. The SQL AGGREGATE function can be used to get summary information for every group and these are applied to individual group. The main importance of GROUP BY clause is to summarizing of data from database, so these commands are frequently used in the reporting queries. Only one result is returned after the executing the GROUP BY clause & these queries are called as grouped queries.

You can use the WHERE clause along with GROUP BY clause, but WHERE condition is used to limit the records from the tables & GROUP BY clause is use to group the retrieved result set based on column name specified. If you want to filter the grouped result set then we can use the HAVING clause. This is used after the GROUP BY clause.

SQL GROUP BY Clause Syntax:

SELECT * from Table_Name

GROUP BY Column_Name1,

[Column_Name2,….]

[HAVING CONDITION];

· [SELECT * from Table_Name] – This is regular SELECT command to get the records from database.

· GROUP BY Column_Name1 – This is clause is used to group the result set based column name specified. Here you can specify one or more column names.

· [Column_Name2,….] – This is optional. In the GROUP BY clause, one column name is mandatory on which you have to group the result set. If you specify more than one column name then result set first group on first column value & then next column(s).

· [HAVING CONDITION] – This Clause used to filter out the result data set based on “CONDITION”. You can specify any condition using HAVING clause

In this tutorial we have created a sample Employees table on which we are executing the different SQL GROUP BY queries,

Using GROUP BY with Aggregate Functions:

The use of AGGREGATE functions is very much powerful when we use then along with GROUP BY clause. In the SQL GROUP BY queries, the most of times GROUP BY clauses are used with AGGREGATE functions.

Here we are going to see different GROUP BY Clause example with different combinations of the AGGREGATE Functions:

SQL GROUP BY with SUM() function
SQL GROUP BY with COUNT() function
SQL GROUP BY with COUNT() and SUM()
SQL GROUP BY on more than one column
SQL GROUP BY with WHERE clause
SQL GROUP BY with HAVING clause

1) SQL GROUP BY with SUM() function:

Suppose user want to get the sum of Salary paid to each department, so in the Employees table we have column called DEPARTMENT_ID & SALARY columns. So we can group the result set using DEPARTMENT_ID & we will use the SUM Aggregate function to get sum of salary by each department.

SELECT DEPARTMENT_ID,

SUM(SALARY) as Total_Salary

FROM Employees

GROUP BY DEPARTMENT_ID;

Following is the result upon executing the above SQL GROUP BY query

2) SQL GROUP BY with COUNT() function:

Suppose user wants to get the number employees in each department, so in the Employees table we have column called DEPARTMENT_ID. So we can group the result set using DEPARTMENT_ID & we will use the COUNT Aggregate function to get number of employees by each department.

SELECT DEPARTMENT_ID,

COUNT(*) as Number_Of_Emloyees

FROM Employees

GROUP BY DEPARTMENT_ID;

Following is the result upon executing the above SQL GROUP BY query,

3) SQL GROUP BY with COUNT() and SUM() function:

Suppose user wants to get the number employees in each department & sum of Salary paid to each department, so in the Employees table we have column called DEPARTMENT_ID and SALARY. So we can group the result set using DEPARTMENT_ID & we will use COUNT() & SUM() Aggregate functions. COUNT() is used to get the number of employees by each department & SUM() is used to get the sum of

SELECT DEPARTMENT_ID,

COUNT(*) as Number_Of_Emloyees,

SUM(SALARY)

FROM Employees

GROUP BY DEPARTMENT_ID;

Following is the result upon executing the above SQL GROUP BY query,

4) SQL GROUP BY on more than one column:

Group by Department id, Job Id & & SUM of salary with department

Suppose user wants to get the number employees in each department & sum of Salary paid to each department by Job ID, so in the Employees table we have column called DEPARTMENT_ID, SALARY and Job_ID. So here first we can group the result set using DEPARTMENT_ID & then by JOB_ID. Also we will use the SUM() Aggregate function to get the sum of salary by each Job_id within each department.

SELECT DEPARTMENT_ID,

JOB_ID,

SUM(SALARY)

FROM Employees

GROUP BY DEPARTMENT_ID, JOB_ID;

Following is the result upon executing the above SQL GROUP BY query,

5) SQL GROUP BY with WHERE clause:

Suppose user wants to get the sum of Salary paid to DEPARTMENT_ID = 50, so in the Employees table we have column called DEPARTMENT_ID and SALARY. So here first we will use the WHERE condition on DEPARTMENT_ID = 50, this fitters the result set & returns only records from employee table related to DEPARTMENT_ID = 50. Next to WHERE clause, we can group the result set using DEPARTMENT_ID.

SELECT DEPARTMENT_ID,

SUM(SALARY)

FROM Employees

WHERE DEPARTMENT_ID = 50

GROUP BY DEPARTMENT_ID;

Following is the result upon executing the above SQL GROUP BY query,

6) SQL GROUP BY with HAVING clause:

Group by Department id & count of employee with department & HAVING count > 1

Suppose user wants to get the number of employees from each department where at least two employee present in department. So we can group the result set using DEPARTMENT_ID & we will use COUNT()Aggregate function to get the number of employees by each department.

Here we will use HAVING clause to get the employee count > 1

SELECT DEPARTMENT_ID,

COUNT(*) as Number_Of_Emloyees

FROM Employees

GROUP BY DEPARTMENT_ID

HAVING COUNT(*) > 1;

Following is the result upon executing the above SQL GROUP BY query,

Conclusion on SQL GROUP BY Clause:

The SQL GROUP BY clause is used to divide the result set into smaller groups.
The grouping can happen after retrieves the rows from a table.
In the GROUP BY Clause the grouping is done using same values present in the result set.
The GROUP BY Clause is used with the conjunction of SQL SELECT query.
The WHERE clause is used to retrieve rows based on a certain condition, but it cannot be applied to grouped result.
The HAVING clause is used to filter the result set of GROUP BY clause. This is used after GROUP BY clause.

Learning JOINs in MySQL database with examples

What is a JOIN?

An SQL JOIN clause is used to query data from two or more tables from a MySQL database or in other words by using JOINs you can join one or more tables.

How many types of JOIN in MySQL?

Wikipedia says: According to ANSI standard there are 4 types of JOIN. 1.INNER 2.OUTER 3.LEFT 4.RIGHT As a special case, there is one more JOIN called SELF-JOIN which means a table can JOIN to itself is a SELF-JOIN. Lets see the two tables which i am going to use in my example. The 2 tables namely people and property from a database called phphunger.

Step 1:

First create 2 tables (people and property) and insert the dump data with the following code.

CREATE TABLE IF NOT EXISTS `people` (

`id` int(10) NOT NULL AUTO_INCREMENT,

`name` varchar(50) NOT NULL,

`phone` int(12) NOT NULL,

PRIMARY KEY (`id`)

) ENGINE=MyISAM;

INSERT INTO `people` (`id`, `name`, `phone`) VALUES

(1, 'phphunger', 1234567890),

(2, 'Larry Page', 1236547890),

(3, 'Steve Jobs', 1235468790),

(4, 'Mark Zukerberg', 1239874560);

CREATE TABLE IF NOT EXISTS `property` (

`id` int(10) NOT NULL,

`pid` int(10) NOT NULL,

`website` varchar(25) NULL

) ENGINE=MyISAM DEFAULT CHARSET=latin1;

INSERT INTO `property` (`id`, `pid`, `website`) VALUES

(1, 1, 'www.phphunger.com'),

(2, 2, 'www.google.com'),

(2, 3, 'www.gmail.com'),

(2, 4, 'www.youtube.com'),

(3, 5, NULL),

(4, 6, 'www.facebook.com'),

(5, 7, 'www.twitter.com'),

(6, 8, 'www.linkedin.com');

Step 2:

Applying different JOINs for the created tables.

CASE 1:

Applying Regular JOIN for the 2 tables. (Regular JOIN means INNER JOIN or JOIN). Before applying JOINs to the tables lets first see what's the functionality of JOIN.

SELECT name, phone, website

FROM people

JOIN property ON people.id = property.id

LIMIT 0 , 30

Functionality of a JOIN (INNER JOIN or Regular JOIN):
If you perform a JOIN on the 2 tables then you will get all the matched records and the unmatched records will not be displayed.

Lets see the output after applying JOIN

Observation : From the above output you can judge that i have filtered the records based on their id's. So from this filtering i have obtained the matched records from both the tables. Unmatched records are not displayed here.

CASE 2:
Applying LEFT JOIN for both the tables. Before applying LEFT JOIN to the tables lets first see what's the functionality of LEFT JOIN.

Functionality of a LEFT JOIN:

If you perform a LEFT JOIN on the 2 tables then you will get all the matched records as well as you will get an extra record for each unmatched record from the left table of the JOIN. Means from my example each column name "name" gets a mention.

SELECT name, phone, website

FROM people

LEFT JOIN property ON people.id = property.id

LIMIT 0 , 30

Lets see the output.

CASE 4:
Applying RIGHT OUTER JOIN for both the tables. Before applying RIGHT OUTER JOIN to the tables lets first see what's the functionality of RIGHT OUTER JOIN. Functionality of RIGHT OUTER JOIN:

RIGHT OUTER JOIN is same as RIGHT JOIN. Adding OUTER after the clause RIGHT to yield the result. Lets see the example.

SELECT name, phone, website

FROM people

RIGHT OUTER JOIN property ON people.id = property.id

LIMIT 0 , 30

CASE 5:
Applying LEFT OUTER JOIN for both the tables. Before applying LEFT OUTER JOIN to the tables lets first see what's the functionality of LEFT OUTER JOIN.
Functionality of LEFT OUTER JOIN:

LEFT OUTER JOIN is same as LEFT JOIN. Adding OUTER after the clause LEFT to yield the result.
Lets see the example.

SELECT name, phone, website

FROM people

LEFT OUTER JOIN property ON people.id = property.id

LIMIT 0 , 30

1. Inner Join or Equi join

2. Self Join

2. Outer Join

   outer join is again classified into

   a) Left Outer Join

   b) Right Outer Join

   c) Full Outer Join

3. Cross join

Difference between MySQL delete and truncate table

TRUNCATE vs DELETE

TRUNCATE	DELETE
TRUNCATE is a DDL command	DELETE is a DML command
TRUNCATE is executed using a table lock and whole table is locked for remove all records.	DELETE is executed using a row lock, each row in the table is locked for deletion.
We cannot use Where clause with TRUNCATE.	We can use where clause with DELETE to filter & delete specific records.
TRUNCATE removes all rows from a table.	The DELETE command is used to remove rows from a table based on WHERE condition.
Minimal logging in transaction log, so it is performance wise faster.	It maintain the log, so it slower than TRUNCATE.
TRUNCATE TABLE removes the data by deallocating the data pages used to store the table data and records only the page deallocations in the transaction log.	The DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row
Identify column is reset to its seed value if table contains any identity column.	Identity of column keep DELETE retain the identity
To use Truncate on a table you need at least ALTER permission on the table.	To use Delete you need DELETE permission on the table.
Truncate uses the less transaction space than Delete statement.	Delete uses the more transaction space than Truncate statement.
Truncate cannot be used with indexed views	Delete can be used with indexed views
Drop all object’s statistics and marks like High Water Mark free extents and leave the object really empty with the first extent. zero pages are left in the table	Keeps object’s statistics and all allocated space. After a DELETE statement is executed, the table can still contain empty pages.
TRUNCATE TABLE can’t activate a trigger because the operation does not log individual row deletions. When we run truncate command to remove all rows of table then it actually doesn’t removes any row, rather it deallocates the data pages. In case of Truncate triggers will not be fired because no modification takes place, we have just deallocated the data pages not deleted any row from table.	Delete activates a trigger because the operation are logged individually. When we execute Delete command, DELETE trigger will be initiated if present. Delete is a DML command and it deletes the data on row-by-row basis from a table. Which means delete is modifying the data by deleting it from the table. Triggers are fired when a DML statement executed on a table, so trigger will be fired in case of Delete command execution.

Both remove records from the table, so what is the difference. Very simple, read along.

For this article, I will use a ‘friends’ table.

delete from friends;

and

truncate table friends;

Both the above statements remove all records from the table, but the essentially difference is as follows.

delete from friends – will delete all records from the friends table. That’s it. I.e. the auto_increment counter does not get reset.

truncate table friends – will delete all records from the table and also rebuild the table, thus resetting the auto_increment counter.

Try these steps to identify yourself:

Step 1:

create table friends (
id int not null primary key auto_increment,
name varchar(20)
);

Step 2:
insert into friends (name) values (‘Sunil’);
insert into friends (name) values (‘Vishal’);
insert into friends (name) values (‘Vikram’);

Step 3:
select * from friends;

Note the id of the last record. It will be 3.

Step 4:
delete from friends;

Step 5:
insert into friends (name) values (‘Mithil’);

Step 6:
select * from friends;

Note that the id of the only record will be 4. This means that delete from friends removed all records, but did not reset the auto_increment counter.

Step 7:
Repeat Step 2 – 3 and goto step 8.

Step 8:
truncate table friends;

Step 9:
Repeat step 5 – 6 and goto step 10.

Note that after you repeat step 6, you will see that the only record i.e. of Mithil has id 1. This means that truncate deletes all the records from the table and resets the auto_increment pointer to start from 1.

. Delete use for delete row by row but truncate will delete the entire table.
2. In Truncate rollback not possible.
3. Value of Auto Increment will reset from starting after use of Truncate not in Delete.
4. Truncate is a DDL command and Delete is a Dml command.
5. When Delete the Particular row the Corresponding Delete Trigger(if exists) Fire.
In Case of Truncate the Trigger is not fired.

What is the difference between explode and split?

Both the functions are used to Split a string. Explode is used to split a string using another string.

Explode- The explode() function splits the string by string.

E.g explode (" this", "this is a string"); will return “Is a string”
$st = "Test your PHP code online, right here";

$spl=explode(" ", $st);

print_r($spl)."\n";

$im = implode(" ", $spl);

print_r($im)."\n";

Output

Array //Explode function use.
(
[0] => Test
[1] => your
[2] => PHP
[3] => code
[4] => online,
[5] => right
[6] => here
)
Test your PHP code online, right here // after implode() function use.

Split is used to split a string using a regular expression

$date = "04/03/2015";

$result = split("/", $date);

print_r($result);

Output

Array
(
[0] => 04
[1] => 03
[2] => 2015
)

Both the functions are used to Split a string. However, Split is used to split a string using a regular expression. On the other hand, Explode is used to split a string using another string.

E.g explode (" this", "this is a string"); will return “Is a string”
Split (" + ", "This+ is a string")

What’s the difference between using the GET method versus POST?

GET:

Parameters remain in browser history because they are part of the URL
Can be bookmarked.
GET method should not be used when sending passwords or other sensitive information.
7607 character maximum size.
Url example: page2.php?category=sport

POST:

Parameters are not saved in browser history.
Can not be bookmarked.
POST method used when sending passwords or other sensitive information.
8 Mb max size for the POST method.
Url example: page2.php

	GET (HTTP)	POST (HTTP)
History	Parameters remain in browser history because they are part of the URL	Parameters are not saved in browser history.
Bookmarked	Can be bookmarked.	Can not be bookmarked.
BACK button/re-submit behaviour	GET requests are re-executed but may not be re-submitted to server if the HTML is stored in the browser cache.	The browser usually alerts the user that data will need to be re-submitted.
Encoding type (enctype attribute)	application/x-www-form-urlencoded	multipart/form-data or application/x-www-form-urlencoded Use multipart encoding for binary data.
Parameters	can send but the parameter data is limited to what we can stuff into the request line (URL). Safest to use less than 2K of parameters, some servers handle up to 64K	Can send parameters, including uploading files, to the server.
Hacked	Easier to hack for script kiddies	More difficult to hack
Restrictions on form data type	Yes, only ASCII characters allowed.	No restrictions. Binary data is also allowed.
Security	GET is less secure compared to POST because data sent is part of the URL. So it's saved in browser history and server logs in plaintext.	POST is a little safer than GET because the parameters are not stored in browser history or in web server logs.
Restrictions on form data length	Yes, since form data is in the URL and URL length is restricted. A safe URL length limit is often 2048 characters but varies by browser and web server.	No restrictions
Usability	GET method should not be used when sending passwords or other sensitive information.	POST method used when sending passwords or other sensitive information.
Visibility	GET method is visible to everyone (it will be displayed in the browser's address bar) and has limits on the amount of information to send.	POST method variables are not displayed in the URL.
Cached	Can be cached	Not cached
Large variable values	7607 character maximum size.	8 Mb max size for the POST method.

Difference between “include” and “require” in php

require will throw a PHP Fatal Error if the file cannot be loaded. (Execution stops)

include produces a Warning if the file cannot be loaded. (Execution continues)

· include_once and require_once do the same thing, but only if the file was not already loaded.

Difference: Website vs Web Application

Web Site : -
1)A Website is Informational
2)All the files in folder structure are automatically included in the website. There is no .csproj/.vbproj project files in Website
3)When you deploy or publish Website, you need to upload both .aspx and .cs/.vb files to the server
4)By default explicit namespaces are not added to pages, controls or classes, but you can add them manually
5)There is no need to re-compile or built the website before publish or deployment
Web Application :-
1)A Web Application is Interactive
2)A Visual Studio .csproj/.vbproj project file stores information about the Web Application, such as list of included project files or any internal or external project to project references
3)When you deploy or publish Web Application, you only need to upload .aspx files and there is no need to upload .cs/.vb files because code-behind files are pre-compiled in .dll file
4)By default explicit namespaces are added to pages, controls and classes
5)You need to re-compile or built the web application before publish or deployment because it contains .dll files with reference of other project file details

What is the difference between Stored Procedures and triggers?

Trigger
We can execute a stored procedure whenever we want with the help of the exec command, but a trigger can only be executed whenever an event (insert, delete, and update) is fired on the table on which the trigger is defined.
We can call a stored procedure from inside another stored procedure but we can't directly call another trigger within a trigger. We can only achieve nesting of triggers in which the action (insert, delete, and update) defined within a trigger can initiate execution of another trigger defined on the same table or a different table.
Stored procedures can be scheduled through a job to execute on a predefined time, but we can't schedule a trigger.
Stored procedure can take input parameters, but we can't pass parameters as input to a trigger.
Stored procedures can return values but a trigger cannot return a value.
We can use Print commands inside a stored procedure for debugging purposes but we can't use print commands inside a trigger.
We can use transaction statements like begin transaction, commit transaction, and rollback inside a stored procedure but we can't use transaction statements inside a trigger.
We can call a stored procedure from the front end (.asp files, .aspx files, .ascx files, etc.) but we can't call a trigger from these files.
Stored procedures are used for performing tasks. Stored procedures are normally used for performing user specified tasks. They can have parameters and return multiple results sets.
The Triggers for auditing work: Triggers normally are used for auditing work. They can be used to trace the activities of table events.

No1

1) Stored Procedure is predefined collection of sql statements.
2) Stored Procedure is Precompiled Execution.
3) Trigger is not Precompiled Exectution.
4) Trigger is not Reduce Client / Server Network Traffic.
5) Trigger Execute Automatic Execution Process. Stored Procedure is not automatic Procedure process.

No2

1. Stored Procedure can be run independently
The triggers executes based on table events
2. The Stored Procedures are used for performing tasks
The Triggers for auditing work
3. The Stored Procedures can have the parameters
The Triggers cannot have any parameters
4. The Stored Procedure cannot call triggers
The triggers can call Stored Procedures

What is the difference between Code Igniter and Cake PHP?

CakePHP and Codeigniter are two most popular PHP frameworks. I’m going to compare both of these frameworks here:
1. Simplicity:
CodeIgniter: CodeIgniter is simple and not too strict to work with.
CakePHP: CakePHP is not so simple as CodeIgniter. It is also a bit strict and most of its simplicity comes via automation.
2. Ajax:
CodeIgniter: CodeIgniter doesn’t have any Ajax helper.
CakePHP: CakePHP comes with Ajax helper.
3. Code Generation:
CodeIgniter: CodeIgniter doesn’t have any code generation or console features.
CakePHP: CakePHP’s ‘Bake Console’ can create any of CakePHP’s basic ingredients: Models, Controllers, Views. It can basically create a fully functional application in minutes.
4. Plugins:
CodeIgniter: There aren’t many plugins available for CodeIgniter as compared to CakePHP.
CakePHP: Good amount of plugins are available for CakePHP as compared to CodeIgniter.
5. PHP Version:
CodeIgniter: CodeIgniter although runs on PHP 4 and PHP 5, doesn’t take advantage of PHP 5 object oriented features.
CakePHP: CakePHP version 2.0 runs only on PHP 5.2 which definitely takes advantage of PHP 5′s Object Oriented features.

Cash Study->

=> We have three tables like students, events and proprietary.

evt_id	Evt_name
1	Music
2	Dance
3	Song
4	Sports

=> Students Events Proprietary

pty_id	Std_id	Evt_id
1	3	1
2	4	2
3	2	3
4	1	4

Std_id	Std_name
1	Jon
2	Smith
3	Pradeep
4	Ramesh

Output look like this

Pty_id	Std_Name	Std_id	Evt_Name	Evt_id
1	Pradeep	3	Music	1
2	Ramesh	4	Dance	2
3	Smith	2	Song	3
4	Jon	1	Sports	4

Query 1-> SELECT pty.pty_id, std.std_name, std.std_id, evt.evt_name, evt.evt_id FROM students std, events evt , proprietary pty WHERE pty.evt_id=evt.evt_id and pty.std_id=std.std_id order by pty.pty_id;

--------+----------+--------+
| emp_id | emp_name | salary |
+--------+----------+--------+
| 1 | James | 2000 |
| 2 | Jack | 4000 |
| 3 | Henry | 6000 |
| 4 | Tom | 8000 |
+--------+----------+--------+
4 rows IN SET (0.00 sec)

mysql> SELECT * FROM Department;
+---------+-----------+
| dept_id | dept_name |
+---------+-----------+
| 101 | Sales |
| 102 | Marketing |
| 103 | Finance |
+---------+-----------+
3 rows IN SET (0.00 sec)

mysql> SELECT * FROM Register;
+--------+---------+
| emp_id | dept_id |
+--------+---------+
| 1 | 101 |
| 2 | 102 |
| 3 | 103 |
| 4 | 102 |
+--------+---------+
4 rows IN SET (0.00 sec)

mysql> SELECT emp_name, dept_name FROM Employee e JOIN Register r ON e.emp_id=r.emp_id JOIN Department d ON r.dept_id=d.dept_id;
+----------+-----------+
| emp_name | dept_name |
+----------+-----------+
| James | Sales |
| Jack | Marketing |
| Henry | Finance |
| Tom | Marketing |
+----------+-----------+
4 rows IN SET (0.01 sec)

Program in C

2015-04-09T03:46:00.004-07:00

    *
   *** 
  *****
 *******
*********

#include <stdio.h>

int main()
{
   int i, j, k;
   for(i=1;i<=5;i++)
   {
       for(j=i;j<5;j++)
       {
           printf(" ");
       }
       for(k=1;k<(i*2);k++)
       {
               printf("*");
       }
       printf("\n");
   }

   return 0;
}

What is AJAX?

2015-04-02T04:47:00.002-07:00

AJAX stands for Asynchronous JavaScript and XML. AJAX is a new technique for creating better, faster, and more interactive web applications with the help of XML, HTML, CSS, and Java Script.
Ajax uses XHTML for content, CSS for presentation, along with Document Object Model and JavaScript for dynamic content display.
Conventional web applications transmit information to and from the sever using synchronous requests. It means you fill out a form, hit submit, and get directed to a new page with new information from the server.
With AJAX, when you hit submit, JavaScript will make a request to the server, interpret the results, and update the current screen. In the purest sense, the user would never know that anything was even transmitted to the server.
XML is commonly used as the format for receiving server data, although any format, including plain text, can be used.
AJAX is a web browser technology independent of web server software.
A user can continue to use the application while the client program requests information from the server in the background.
Intuitive and natural user interaction. Clicking is not required, mouse movement is a sufficient event trigger.
Data-driven as opposed to page-driven.

Rich Internet Application Technology

AJAX is the most viable Rich Internet Application (RIA) technology so far. It is getting tremendous industry momentum and several tool kit and frameworks are emerging. But at the same time, AJAX has browser incompatibility and it is supported by JavaScript, which is hard to maintain and debug.

AJAX is Based on Open Standards

AJAX is based on the following open standards:

Browser-based presentation using HTML and Cascading Style Sheets (CSS).
Data is stored in XML format and fetched from the server.
Behind-the-scenes data fetches using XMLHttpRequest objects in the browser.
JavaScript to make everything happen.

AJAX - Technologies

AJAX cannot work independently. It is used in combination with other technologies to create interactive webpages.

JavaScript

Loosely typed scripting language.

JavaScript function is called when an event occurs in a page.

Glue for the whole AJAX operation.

DOM

API for accessing and manipulating structured documents.

Represents the structure of XML and HTML documents.

CSS

Allows for a clear separation of the presentation style from the content and may be changed programmatically by JavaScript.

XMLHttpRequest

JavaScript object that performs asynchronous interaction with the server.

AJAX - Examples
Here is a list of some famous web applications that make use of AJAX.

Google Maps

A user can drag an entire map by using the mouse, rather than clicking on a button.

http://maps.google.com/

Google Suggest

As you type, Google will offer suggestions. Use the arrow keys to navigate the results.

http://www.google.com/webhp?complete=1&hl=en

Gmail

Gmail is a webmail, built on the idea that email can be more intuitive, efficient and useful.

http://gmail.com/

Yahoo Maps (new)

Now it's even easier and more fun to get where you're going!

http://maps.yahoo.com/

Difference in AJAX and Conventional CGI Program

Try these two examples one by one and you will feel the difference. While trying AJAX example, there is not discontinuity and you get the response very quickly, but when you try the standard GCI example, you would have to wait for the response and your page also gets refreshed.

AJAX Example:

Top of Form

* =

Bottom of Form

Top of Form

Bottom of Form

Standard Example:

Top of Form

* =

Bottom of Form

Top of Form

Bottom of Form

NOTE: We have given a more complex example in AJAX Database.

AJAX - Browser Support
All the available browsers cannot support AJAX. Here is a list of major browsers, that support AJAX.

Mozilla Firefox 1.0 and above.

Netscape version 7.1 and above.

Apple Safari 1.2 and above.

Microsoft Internet Explorer 5 and above.

Konqueror.

Opera 7.6 and above.

When you write your next application, do consider the browsers that do not support AJAX.

NOTE: When we say that a browser does not support AJAX, it simply means that the browser does not support creation of Javascript object XMLHttpRequest object.

Writing Browser Specific Code

The Simplest way to make your source code compatible with a browser is to use try...catch blocks in your JavaScript.

<html>

<body>

   <script language="javascript" type="text/javascript">

   

   </script>



   <form name='myForm'>

      Name: <input type='text' name='username' /> <br />

      Time: <input type='text' name='time' />

   </form>



</body>

</html>

In the above JavaScript code, we try three times to make our XMLHttpRequest object. Our first attempt:

ajaxRequest = new XMLHttpRequest();

It is for Opera 8.0+, Firefox, and Safari browsers. If it fails, we try two more times to make the correct object for an Internet Explorer browser with:

ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");

ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");

If it doesn't work, then we can use a very outdated browser that doesn't support XMLHttpRequest, which also means it doesn't support Ajax.

Most likely though, our variable ajaxRequest will now be set to whatever XMLHttpRequest standard the browser uses and we can start sending data to the server. The step-wise AJAX workflow is explained in the next chapter.

AJAX - Action
This chapter gives you a clear picture of the exact steps of AJAX operation.

Steps of AJAX Operation

A client event occurs.

An XMLHttpRequest object is created.

The XMLHttpRequest object is configured.

The XMLHttpRequest object makes an asynchronous request to the Webserver.

The Webserver returns the result containing XML document.

The XMLHttpRequest object calls the callback() function and processes the result.

The HTML DOM is updated.

Let us take these steps one by one.

A Client Event Occurs

A JavaScript function is called as the result of an event.

Example: validateUserId() JavaScript function is mapped as an event handler to an onkeyup event on input form field whose id is set to "userid"

<input type="text" size="20" id="userid" name="id" onkeyup="validateUserId();">.

The XMLHttpRequest Object is Created

var ajaxRequest; // The variable that makes Ajax possible!

function ajaxFunction(){

   try{



      // Opera 8.0+, Firefox, Safari

      ajaxRequest = new XMLHttpRequest();

   }catch (e){



      // Internet Explorer Browsers

      try{

         ajaxRequest = new ActiveXObject("Msxml2.XMLHTTP");

      }catch (e) {



         try{

            ajaxRequest = new ActiveXObject("Microsoft.XMLHTTP");

         }catch (e){



            // Something went wrong

            alert("Your browser broke!");

          return false;

         }

      }

   }

}

The XMLHttpRequest Object is Configured

In this step, we will write a function that will be triggered by the client event and a callback function processRequest() will be registered.

function validateUserId() {

   ajaxFunction();



   // Here processRequest() is the callback function.

   ajaxRequest.onreadystatechange = processRequest;



   if (!target) target = document.getElementById("userid");

   var url = "validate?id=" + escape(target.value);



ajaxRequest.open("GET", url, true);

   ajaxRequest.send(null);

}

Making Asynchronous Request to the Webserver

Source code is available in the above piece of code. Code written in bold typeface is responsible to make a request to the webserver. This is all being done using the XMLHttpRequest object ajaxRequest.

function validateUserId() {

   ajaxFunction();



   // Here processRequest() is the callback function.

   ajaxRequest.onreadystatechange = processRequest;



   if (!target) target = document.getElementById("userid");

   var url = "validate?id=" + escape(target.value);



   ajaxRequest.open("GET", url, true);

   ajaxRequest.send(null);

}

Assume you enter Zara in the userid box, then in the above request, the URL is set to "validate?id=Zara".

Webserver Returns the Result Containing XML Document

You can implement your server-side script in any language, however its logic should be as follows.

Get a request from the client.

Parse the input from the client.

Do required processing.

Send the output to the client.

If we assume that you are going to write a servlet, then here is the piece of code.

public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException

{

   String targetId = request.getParameter("id");



   if ((targetId != null) && !accounts.containsKey(targetId.trim()))

   {

      response.setContentType("text/xml");

      response.setHeader("Cache-Control", "no-cache");

      response.getWriter().write("true");

   }

   else

   {

      response.setContentType("text/xml");

      response.setHeader("Cache-Control", "no-cache");

      response.getWriter().write("false");

   }

}

Callback Function processRequest() is Called

The XMLHttpRequest object was configured to call the processRequest() function when there is a state change to the readyState of the XMLHttpRequest object. Now this function will receive the result from the server and will do the required processing. As in the following example, it sets a variable message on true or false based on the returned value from the Webserver.

function processRequest() {

   if (req.readyState == 4) {

      if (req.status == 200) {

         var message = ...;

...

}

The HTML DOM is Updated

This is the final step and in this step, your HTML page will be updated. It happens in the following way:

JavaScript gets a reference to any element in a page using DOM API.

The recommended way to gain a reference to an element is to call.

document.getElementById("userIdMessage"),

// where "userIdMessage" is the ID attribute

// of an element appearing in the HTML document

JavaScript may now be used to modify the element's attributes; modify the element's style properties; or add, remove, or modify the child elements. Here is an example:

<script type="text/javascript">



</script>

<body>

<div id="userIdMessage"><div>

</body>

If you have understood the above-mentioned seven steps, then you are almost done with AJAX. In the next chapter, we will see XMLHttpRequest object in more detail.

AJAX - XMLHttpRequest
The XMLHttpRequest object is the key to AJAX. It has been available ever since Internet Explorer 5.5 was released in July 2000, but was not fully discovered until AJAX and Web 2.0 in 2005 became popular.

XMLHttpRequest (XHR) is an API that can be used by JavaScript, JScript, VBScript, and other web browser scripting languages to transfer and manipulate XML data to and from a webserver using HTTP, establishing an independent connection channel between a webpage's Client-Side and Server-Side.

The data returned from XMLHttpRequest calls will often be provided by back-end databases. Besides XML, XMLHttpRequest can be used to fetch data in other formats, e.g. JSON or even plain text.

You already have seen a couple of examples on how to create an XMLHttpRequest object.

Listed below is listed are some of the methods and properties that you have to get familiar with.

XMLHttpRequest Methods

abort()

Cancels the current request.

getAllResponseHeaders()

Returns the complete set of HTTP headers as a string.

getResponseHeader( headerName )

Returns the value of the specified HTTP header.

open( method, URL )

open( method, URL, async )

open( method, URL, async, userName )

open( method, URL, async, userName, password )

Specifies the method, URL, and other optional attributes of a request.

The method parameter can have a value of "GET", "POST", or "HEAD". Other HTTP methods, such as "PUT" and "DELETE" (primarily used in REST applications) may be possible.

The "async" parameter specifies whether the request should be handled asynchronously or not. "true" means that the script processing carries on after the send() method without waiting for a response, and "false" means that the script waits for a response before continuing script processing.

send( content )

Sends the request.

setRequestHeader( label, value )

Adds a label/value pair to the HTTP header to be sent.

XMLHttpRequest Properties

onreadystatechange

An event handler for an event that fires at every state change.

readyState

The readyState property defines the current state of the XMLHttpRequest object.

The following table provides a list of the possible values for the readyState property:

State

Description

0

The request is not initialized.

1

The request has been set up.

2

The request has been sent.

3

The request is in process.

4

The request is completed.

readyState = 0 After you have created the XMLHttpRequest object, but before you have called the open() method.

readyState = 1 After you have called the open() method, but before you have called send().

readyState = 2 After you have called send().

readyState = 3 After the browser has established a communication with the server, but before the server has completed the response.

readyState = 4 After the request has been completed, and the response data has been completely received from the server.

responseText

Returns the response as a string.

responseXML

Returns the response as XML. This property returns an XML document object, which can be examined and parsed using the W3C DOM node tree methods and properties.

status

Returns the status as a number (e.g., 404 for "Not Found" and 200 for "OK").

statusText

Returns the status as a string (e.g., "Not Found" or "OK").

AJAX - Database Operations
To clearly illustrate how easy it is to access information from a database using AJAX, we are going to build MySQL queries on the fly and display the results on "ajax.html". But before we proceed, let us do the ground work. Create a table using the following command.

NOTE: We are assuming you have sufficient privilege to perform the following MySQL operations

CREATE TABLE 'ajax_example' (

   'name' varchar(50) NOT NULL,

   'age' int(11) NOT NULL,

   'sex' varchar(1) NOT NULL,

   'wpm' int(11) NOT NULL,

   PRIMARY KEY ('name')

)

Now dump the following data into this table using the following SQL statements:

INSERT INTO 'ajax_example' VALUES ('Jerry', 120, 'm', 20);

INSERT INTO 'ajax_example' VALUES ('Regis', 75, 'm', 44);

INSERT INTO 'ajax_example' VALUES ('Frank', 45, 'm', 87);

INSERT INTO 'ajax_example' VALUES ('Jill', 22, 'f', 72);

INSERT INTO 'ajax_example' VALUES ('Tracy', 27, 'f', 0);

INSERT INTO 'ajax_example' VALUES ('Julie', 35, 'f', 90);

Client Side HTML File

Now let us have our client side HTML file, which is ajax.html, and it will have the following code:

<html>

<body>

<script language="javascript" type="text/javascript">



</script>

<form name='myForm'>

   Max Age: <input type='text' id='age' /> <br />

   Max WPM: <input type='text' id='wpm' /> <br />

   Sex:

   <select id='sex'>

      <option value="m">m</option>

      <option value="f">f</option>

   </select>

   <input type='button' onclick='ajaxFunction()' value='Query MySQL'/>



</form>

<div id='ajaxDiv'>Your result will display here</div>

</body>

</html>

NOTE: The way of passing variables in the Query is according to HTTP standard and have formA.

URL?variable1=value1;&variable2=value2;

The above code will give you a screen as given below:

NOTE: This is dummy screen and would not work

Top of Form

Max Age:

Max WPM:

Sex:

Bottom of Form

Top of Form

Bottom of Form

Your result will display here in this section after you have made your entry.

NOTE: This is a dummy screen.

Server Side PHP File

Your client-side script is ready. Now, we have to write our server-side script, which will fetch age, wpm, and sex from the database and will send it back to the client. Put the following code into the file "ajax-example.php".

<?php

$dbhost = "localhost";

$dbuser = "dbusername";

$dbpass = "dbpassword";

$dbname = "dbname";



//Connect to MySQL Server

mysql_connect($dbhost, $dbuser, $dbpass);



//Select Database

mysql_select_db($dbname) or die(mysql_error());



// Retrieve data from Query String

$age = $_GET['age'];

$sex = $_GET['sex'];

$wpm = $_GET['wpm'];



// Escape User Input to help prevent SQL Injection

$age = mysql_real_escape_string($age);

$sex = mysql_real_escape_string($sex);

$wpm = mysql_real_escape_string($wpm);



//build query

$query = "SELECT * FROM ajax_example WHERE sex = '$sex'";

if(is_numeric($age))

   $query .= " AND age <= $age";

if(is_numeric($wpm))

   $query .= " AND wpm <= $wpm";



//Execute query

$qry_result = mysql_query($query) or die(mysql_error());

//Build Result String

$display_string = "<table>";

$display_string .= "<tr>";

$display_string .= "<th>Name</th>";

$display_string .= "<th>Age</th>";

$display_string .= "<th>Sex</th>";

$display_string .= "<th>WPM</th>";

$display_string .= "</tr>";

// Insert a new row in the table for each person returned

while($row = mysql_fetch_array($qry_result)){

   $display_string .= "<tr>";

   $display_string .= "<td>$row[name]</td>";

   $display_string .= "<td>$row[age]</td>";

   $display_string .= "<td>$row[sex]</td>";

   $display_string .= "<td>$row[wpm]</td>";

   $display_string .= "</tr>";

}

echo "Query: " . $query . "<br />";

$display_string .= "</table>";

echo $display_string;

?>

Now try by entering a valid value (e.g., 120) in Max Age or any other box and then click Query MySQL button.

Top of Form

Max Age:

Max WPM:

Sex:

Bottom of Form

Top of Form

Bottom of Form

Your result will display here in this section after you have made your entry.

If you have successfully completed this lesson, then you know how to use MySQL, PHP, HTML, and Javascript in tandem to write AJAX applications.

AJAX - Security
AJAX Security: Server Side
·         AJAX-based Web applications use the same server-side security schemes of regular Web applications.

·         You specify authentication, authorization, and data protection requirements in your web.xml file (declarative) or in your program (programmatic).

·         AJAX-based Web applications are subject to the same security threats as regular Web applications.

AJAX Security: Client Side
·         JavaScript code is visible to a user/hacker. Hacker can use JavaScript code for inferring server-side weaknesses.

·         JavaScript code is downloaded from the server and executed ("eval") at the client and can compromise the client by mal-intended code.

·         Downloaded JavaScript code is constrained by the sand-box security model and can be relaxed for signed JavaScript.

AJAX - Issues
AJAX is growing very fast and that is the reason that it contains many issues with it. We hope with the passes of time, they will be resolved and AJAX will become ideal for web applications. We are listing down a few issues that AJAX currently suffers from.

Complexity is increased

Server-side developers will need to understand that presentation logic will be required in the HTML client pages as well as in the server-side logic.

Page developers must have JavaScript technology skills.

AJAX-based applications can be difficult to debug, test, and maintain

JavaScript is hard to test - automatic testing is hard.

Weak modularity in JavaScript.

Lack of design patterns or best practice guidelines yet.

Toolkits/Frameworks are not mature yet

Most of them are in beta phase.

No standardization of the XMLHttpRequest yet

Future version of IE will address this.

No support of XMLHttpRequest in old browsers

Iframe will help.

JavaScript technology dependency and incompatibility

Must be enabled for applications to function.

Still some browser incompatibilities exist.

JavaScript code is visible to a hacker

Poorly designed JavaScript code can invite security problems.

How to get second-highest salary employees in a table

2015-04-01T23:39:00.001-07:00

- Method 1

select max(salary) from Employees

where salary < (select max(salary) from Employees)

- Method 2

select MAX(salary) from Employees

where salary not in(select MAX(salary) from Employees)

- Method 3

select MAX(salary) from Employees

where salary != (select MAX(salary) from Employees )

-Method 4

SELECT salary from Employee ORDER BY salary DESC LIMIT 1, 1;

Latest jQuery Interview Questions & Answers

2015-01-19T05:12:00.000-08:00

Q1. What is jQuery?
Ans: jQuery is fast, lightweight and feature-rich client side JavaScript Library/Framework which helps in to traverse HTML DOM, make animations, add Ajax interaction, manipulate the page content, change the style and provide cool UI effect. It is one of the most popular client side libraries and as per a survey it runs on every second website.
Q2. Why do we use jQuery?
Ans: Due to following advantages.
Easy to use and learn.
Easily expandable.
Cross-browser support (IE 6.0+, FF 1.5+, Safari 2.0+, Opera 9.0+)
Easy to use for DOM manipulation and traversal.
Large pool of built in methods.
AJAX Capabilities.
Methods for changing or applying CSS, creating animations.
Event detection and handling.
Tons of plug-ins for all kind of needs.
Q3. How JavaScript and jQuery are different?
Ans: JavaScript is a language while jQuery is a library built in the JavaScript language that helps to use the JavaScript language.
Q4. Is jQuery replacement of Java Script?
Ans: No. jQuery is not a replacement of JavaScript. jQuery is a different library which is written on top of JavaScript. jQuery is a lightweight JavaScript library that emphasizes interaction between JavaScript and HTML.
Q5. Is jQuery a library for client scripting or server scripting?
Ans. Client side scripting.
Q6. Does jQuery follow W3C recommendations?
Ans: No.
Q7. What is the basic need to start with jQuery?
Ans: To start with jQuery, one needs to make reference of its library. The latest version of jQuery can be downloaded from jQuery.com.
Q8. Which is the starting point of code execution in jQuery?
Ans: The starting point of jQuery code execution is $(document).ready() function which is executed when DOM is loaded.
Q9. What does dollar sign ($) means in jQuery?
Ans: Dollar Sign is nothing but it's an alias for JQuery. Take a look at below jQuery code.
$(document).ready(function(){
});
Over here $ sign can be replaced with "jQuery" keyword.
jQuery(document).ready(function(){
});
Q10. Can we have multiple document.ready() function on the same page?
Ans: YES. We can have any number of document.ready() function on the same page.
Q11. Can we use our own specific character in the place of $ sign in jQuery?
Ans: Yes. It is possible using jQuery.noConflict().
Q12. Is it possible to use other client side libraries like MooTools, Prototype along with jQuery?
Ans: Yes.
Q13. What is jQuery.noConflict?
Ans: As other client side libraries like MooTools, Prototype can be used with jQuery and they also use $() as their global function and to define variables. This situation creates conflict as $() is used by jQuery and other library as their global function. To overcome from such situations, jQuery has introduced jQuery.noConflict().
jQuery.noConflict();
// Use jQuery via jQuery(...)
jQuery(document).ready(function(){
jQuery("div").hide();
});
You can also use your own specific character in the place of $ sign in jQuery.
var $j = jQuery.noConflict();
// Use jQuery via jQuery(...)
$j(document).ready(function(){
$j("div").hide();
});
Q14. Is there any difference between body onload() and document.ready() function?
Ans: document.ready() function is different from body onload() function for 2 reasons.
1. We can have more than one document.ready() function in a page where we can have only one body onload function.
2. document.ready() function is called as soon as DOM is loaded where body.onload() function is called when everything gets loaded on the page that includes DOM, images and all associated resources of the page.
Q15. What is the difference between .js and .min.js?
Ans: jQuery library comes in 2 different versions Production and Deployment. The deployment version is also known as minified version. So .min.js is basically the
minified version of jQuery library file. Both the files are same as far as functionality is concerned. But .min.js is quite small in size so it loads quickly and saves bandwidth.
Q16. Why there are two different version of jQuery library?
Ans: jQuery library comes in 2 different versions.
1. Production
2. Deployment
The production version is quite useful at development time as jQuery is open source and if you want to change something then you can make those changes in production version. But the deployment version is minified version or compressed version so it is impossible to make changes in it. Because it is compressed, so its size is very less than the production version which affects the page load time.
Q17. What is a CDN?
Ans: A content delivery network or content distribution network (CDN) is a large distributed system of servers deployed in multiple data centers across the Internet. The goal of a CDN is to serve content to end-users with high availability and high performance.
Q18. Which are the popular jQuery CDN? And what is the advantage of using CDN?
Ans: There are 3 popular jQuery CDNs.
1. Google.
2. Microsoft
3. jQuery.
Advantage of using CDN.
It reduces the load from your server.
It saves bandwidth. jQuery framework will load faster from these CDN.
The most important benefit is it will be cached, if the user has visited any site which is using jQuery framework from any of these CDN
Q19. How to load jQuery from CDN?
Ans: Below is the code to load jQuery from all 3 CDNs.
Code to load jQuery Framework from Google CDN
<script type="text/javascript"
src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js">
</script>
Code to load jQuery Framework from Microsoft CDN
<script type="text/javascript"
src="http://ajax.microsoft.com/ajax/jquery/jquery-1.9.1.min.js">
</script>
Code to load jQuery Framework from jQuery Site (EdgeCast CDN)
<script type="text/javascript"
src="http://code.jquery.com/jquery-1.9.1.min.js">
</script>
Q20. How to load jQuery locally when CDN fails?
Ans: It is a good approach to always use CDN but sometimes what if the CDN is down (rare possibility though) but you never know in this world as anything can happen.
Below given jQuery code checks whether jQuery is loaded from Google CDN or not, if not then it references the jQuery.js file from your folder.
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript">
if (typeof jQuery == 'undefined')
{
document.write(unescape("%3Cscript src='Scripts/jquery.1.9.1.min.js' type='text/javascript'%3E%3C/script%3E"));
}
</script>
It first loads the jQuery from Google CDN and then checks the jQuery object. If jQuery is not loaded successfully then it will references the jQuery.js file from hard drive location. In this example, the jQuery.js is loaded from Scripts folder.
Q21. What are selectors in jQuery and how many types of selectors are there?
Ans: To work with an element on the web page, first we need to find them. To find the html element in jQuery we use selectors. There are many types of selectors but basic selectors are:
Name: Selects all elements which match with the given element Name.
#ID: Selects a single element which matches with the given ID
.Class: Selects all elements which match with the given Class.
Universal (*): Selects all elements available in a DOM.
Multiple Elements E, F, G: Selects the combined results of all the specified selectors E, F or G.
Attribute Selector: Select elements based on its attribute value.
Q22. How do you select element by ID in jQuery?
Ans: To select element use ID selector. We need to prefix the id with "#" (hash symbol). For example, to select element with ID "txtName", then syntax would be,
$('#txtName')
Q23. What does $("div") will select?
Ans: This will select all the div elements on page.
Q24. How to select element having a particular class (".selected")?
Ans: $('.selected'). This selector is known as class selector. We need to prefix the class name with "." (dot).
Q25. What does $("div.parent") will select?
Ans: All the div element with parent class.
Q26. What are the fastest selectors in jQuery?
Ans: ID and element selectors are the fastest selectors in jQuery.
Q27. What are the slow selectors in jQuery?
Ans: class selectors are the slow compare to ID and element.
Q28. How jQuery selectors are executed?
Ans: Your last selector is always executed first. For example, in below jQuery code, jQuery will first find all the elements with class ".myCssClass" and after that it will reject all the other elements which are not in "p#elmID".
$("p#elmID .myCssClass");
Q29. Which is fast document.getElementByID('txtName') or $('#txtName')?
Ans: Native JavaScript is always fast. jQuery method to select txtName "$('#txtName')" will internally makes a call to document.getElementByID('txtName'). As jQuery is written on top of JavaScript and it internally uses JavaScript only So JavaScript is always fast.
Q30. Difference between $(this) and 'this' in jQuery?
Ans: this and $(this) refers to the same element. The only difference is the way they are used. 'this' is used in traditional sense, when 'this' is wrapped in $() then it becomes a jQuery object and you are able to use the power of jQuery.
$(document).ready(function(){
$('#spnValue').mouseover(function(){
alert($(this).text());
});
});
In below example, this is an object but since it is not wrapped in $(), we can't use jQuery method and use the native JavaScript to get the value of span element.
$(document).ready(function(){
$('#spnValue').mouseover(function(){
alert(this.innerText);
});
});
Q31. How do you check if an element is empty?
Ans: There are 2 ways to check if element is empty or not. We can check using ":empty" selector.
$(document).ready(function(){
if ($('#element').is(':empty')){
//Element is empty
});
});
Q32. How do you check if an element exists or not in jQuery?
Ans: Using jQuery length property, we can ensure whether element exists or not.
$(document).ready(function(){
if ($('#element').length > 0){
//Element exists
});
});
Q33. What is the use of jQuery .each() function?
Ans: The $.each() function is used to iterate over a jQuery object. The $.each() function can be used to iterate over any collection, whether it is an object or an array.
Q34. What is the difference between jquery.size() and jquery.length?
Ans: jQuery .size() method returns number of element in the object. But it is not preferred to use the size() method as jQuery provide .length property and which does the same thing. But the .length property is preferred because it does not have the overhead of a function call.
Q35. What is the difference between $('div') and $('<div/>') in jQuery?
Ans: $('<div/>') : This creates a new div element. However this is not added to DOM tree unless you don't append it to any DOM element.
$('div') : This selects all div elements present on the page.
Q36. What is the difference between parent() and parents() methods in jQuery?
Ans: The basic difference is the parent() function travels only one level in the DOM tree, where parents() function search through the whole DOM tree.
Q37. What is the difference between eq() and get() methods in jQuery?
Ans: eq() returns the element as a jQuery object. This method constructs a new jQuery object from one element within that set and returns it. That means that you can use jQuery functions on it.
get() return a DOM element. The method retrieve the DOM elements matched by the jQuery object. But as it is a DOM element and it is not a jQuery-wrapped object. So jQuery functions can't be used. Find out more here.
Q38. How do you implement animation functionality?
Ans: The .animate() method allows us to create animation effects on any numeric CSS property. This method changes an element from one state to another with CSS styles. The CSS property value is changed gradually, to create an animated effect.
Syntax is:
(selector).animate({styles},speed,easing,callback)
styles: Specifies one or more CSS properties/values to animate.
duration: Optional. Specifies the speed of the animation.
easing: Optional. Specifies the speed of the element in different points of the animation. Default value is "swing".
callback: Optional. A function to be executed after the animation completes.
Simple use of animate function is,
$("btnClick").click(function(){
$("#dvBox").animate({height:"100px"});
});
Q39. How to disable jQuery animation?
Ans: Using jQuery property "jQuery.fx.off", which when set to true, disables all the jQuery animation. When this is done, all animation methods will immediately set elements to their final state when called, rather than displaying an effect.
Q40. How do you stop the currently-running animation?
Ans: Using jQuery ".stop()" method.
Q41. What is the difference between .empty(), .remove() and .detach() methods in jQuery?
Ans: All these methods .empty(), .remove() and .detach() are used for removing elements from DOM but they all are different.
.empty(): This method removes all the child element of the matched element where remove() method removes set of matched elements from DOM.
.remove(): Use .remove() when you want to remove the element itself, as well as everything inside it. In addition to the elements themselves, all bound events and jQuery data associated with the elements are removed.
.detach(): This method is the same as .remove(), except that .detach() keeps all jQuery data associated with the removed elements. This method is useful when removed elements are to be reinserted into the DOM at a later time.
Find out more here
Q42. Explain .bind() vs .live() vs .delegate() vs .on()
Ans: All these 4 jQuery methods are used for attaching events to selectors or elements. But they all are different from each other.
.bind(): This is the easiest and quick method to bind events. But the issue with bind() is that it doesn't work for elements added dynamically that matches the same selector. bind() only attach events to the current elements not future element. Above that it also has performance issues when dealing with a large selection.
.live(): This method overcomes the disadvantage of bind(). It works for dynamically added elements or future elements. Because of its poor performance on large pages, this method is deprecated as of jQuery 1.7 and you should stop using it. Chaining is not properly supported using this method.
.delegate(): The .delegate() method behaves in a similar fashion to the .live() method, but instead of attaching the selector/event information to the document, you can choose where it is anchored and it also supports chaining.
.on(): Since live was deprecated with 1.7, so new method was introduced named ".on()". This method provides all the goodness of previous 3 methods and it brings uniformity for attaching event handlers.
Find out more here
Q43. What is wrong with this code line "$('#myid.3').text('blah blah!!!');"
Ans: The problem with above statement is that the selectors is having meta characters and to use any of the meta-characters (such as !"#$%&'()*+,./:;<=>?@[\]^`{|}~ ) as a literal part of a name, it must be escaped with with two backslashes: \\. For example, an element with id="foo.bar", can use the selector $("#foo\\.bar").
So the correct syntax is,
$('#myid\\.3').text('blah blah!!!');
Q44. How to create clone of any object using jQuery?
Ans: jQuery provides clone() method which performs a deep copy of the set of matched elements, meaning that it copies the matched elements as well as all of their descendant elements and text nodes.
$(document).ready(function(){
$('#btnClone').click(function(){
$('#dvText').clone().appendTo('body');
return false;
});
});
Q45. Does events are also copied when you clone any element in jQuery?
Ans: As explained in previous question, using clone() method, we can create clone of any element but the default implementation of the clone() method doesn't copy events unless you tell the clone() method to copy the events. The clone() method takes a parameter, if you pass true then it will copy the events as well.
$(document).ready(function(){
$("#btnClone").bind('click', function(){
$('#dvClickme').clone(true).appendTo('body');
});
Q46. What is difference between prop and attr?
Ans: attr(): Get the value of an attribute for the first element in the set of matched elements. Whereas ,.prop(): (Introduced in jQuery 1.6) Get the value of a property for the first element in the set of matched elements.
Attributes carry additional information about an HTML element and come in name="value" pairs. Where Property is a representation of an attribute in the HTML DOM tree. Once the browser parse your HTML code, corresponding DOM node will be created which is an object thus having properties.
attr() gives you the value of element as it was defines in the html on page load. It is always recommended to use prop() to get values of elements which is modified via
JavaScript/jQuery , as it gives you the original value of an element's current state. Find out more here.
Q47. What is event.PreventDefault?
Ans: The event.preventDefault() method stops the default action of an element from happening. For example, prevents a link from following the URL.
Q48. What is the difference between event.PreventDefault and event.stopPropagation?
Ans: event.preventDefault(): Stops the default action of an element from happening.
event.stopPropagation(): Prevents the event from bubbling up the DOM tree, preventing any parent handlers from being notified of the event. For example, if there is a link with a click method attached inside of a DIV or FORM that also has a click method attached, it will prevent the DIV or FORM click method from firing.
Q49. What is the difference between event.PreventDefault and "return false"?
Ans: e.preventDefault() will prevent the default event from occurring, e.stopPropagation() will prevent the event from bubbling up and return false will do both.
Q50. What is the difference between event.stopPropagation and event.stopImmediatePropagation?
Ans: event.stopPropagation() allows other handlers on the same element to be executed, while event.stopImmediatePropagation() prevents every event from running. For example, see below jQuery code block.
$("p").click(function(event){
event.stopImmediatePropagation();
});
$("p").click(function(event){
// This function won't be executed
$(this).css("background-color", "#f00");
});
If event.stopPropagation was used in previous example, then the next click event on p element which changes the css will fire, but in case event.stopImmediatePropagation(), the next p click event will not fire.
Q51. How to check if number is numeric while using jQuery 1.7+?
Ans: Using "isNumeric()" function which was introduced with jQuery 1.7.
Q52. How to check data type of any variable in jQuery?
Ans: Using $.type(Object) which returns the built-in JavaScript type for the object.
Q53. How do you attach an event to element which should be executed only once?
Ans: Using jQuery one() method. This attaches a handler to an event for the element. The handler is executed at most once per element. In simple terms, the attached function will be called only once.
$(document).ready(function() {
$("#btnDummy").one("click", function() {
alert("This will be displayed only once.");
});
});
Q54. Can you include multiple version of jQuery? If yes then how they are executed?
Ans: Yes. Multiple versions of jQuery can be included in same page.
Q55. In what situation you would use multiple version of jQuery and how would you include them?
Ans: Well, it is quite possible that the jQuery plugins which are used are dependent on older version but for your own jQuery code, you would like to use newer version. So because of this dependency, multiple version of jQuery may require sometimes on single page.
Below code shows how to include multiple version of jQuery.
<script type='text/javascript' src='js/jquery_1.9.1.min.js'></script>
<script type='text/javascript'>
var $jq = jQuery.noConflict();
</script>
<script type='text/javascript' src='js/jquery_1.7.2.min.js'></script>
By this way, for your own jQuery code use "$jq", instead of "$" as "$jq" refers to jQuery 1.9.1, where "$" refers to 1.7.2.
Q56. Is it possible to hold or delay document.ready execution for some time?
Ans: Yes, it’s possible. With Release of jQuery 1.6, a new method "jQuery.holdReady(hold)" was introduced. This method allows to delay the execution of document.ready() event. document.ready() event is called as soon as your DOM is ready but sometimes there is a situation when you want to load additional JavaScript or some plugins which you have referenced.
$.holdReady(true);
$.getScript("myplugin.js", function() {
$.holdReady(false);
});
Q57. What is chaining in jQuery?
Ans: Chaining is one of the most powerful features of jQuery. In jQuery, Chaining means to connect multiple functions, events on selectors. It makes your code short and easy to manage and it gives better performance. The chain starts from left to right. So left most will be called first and so on.
$(document).ready(function(){
$('#dvContent').addClass('dummy');
$('#dvContent').css('color', 'red');
$('#dvContent').fadeIn('slow');
});
The above jQuery code sample can be re-written using chaining. See below.
$(document).ready(function(){
$('#dvContent').addClass('dummy')
.css('color', 'red')
.fadeIn('slow');
});
Not only functions or methods, chaining also works with events in jQuery.
Q58. How does caching helps and how to use caching in jQuery?
Ans: Caching is an area which can give you awesome performance, if used properly and at the right place. While using jQuery, you should also think about caching. For example, if you are using any element in jQuery more than one time, then you must cache it. See below code.
$("#myID").css("color", "red");
//Doing some other stuff......
$("#myID").text("Error occurred!");
Now in above jQuery code, the element with #myID is used twice but without caching. So both times jQuery had to traverse through DOM and get the element. But if you have saved this in a variable then you just need to reference the variable. So the better way would be,
var $myElement = $("#myID").css("color", "red");
//Doing some other stuff......
$myElement.text("Error occurred!");
So now in this case, jQuery won't need to traverse through the whole DOM tree when it is used second time. So in jQuery, Caching is like saving the jQuery selector in a variable. And using the variable reference when required instead of searching through DOM again.
Q59. You get "jquery is not defined" or "$ is not defined" error. What could be the reason?
Ans: There could be many reasons for this.
You have forgotten to include the reference of jQuery library and trying to access jQuery.
You have included the reference of the jQuery file, but it is after your jQuery code.
The order of the scripts is not correct. For example, if you are using any jQuery plugin and you have placed the reference of the plugin js before the jQuery library then you will face this error.
Q60. How to write browser specific code using jQuery?
Ans: Using jQuery.browser property, we can write browser specific code. This property contains flags for the useragent, read from navigator.userAgent. This property was removed in jQuery 1.9.
Q61. Can we use jQuery to make ajax request?
Ans: Yes. jQuery can be used for making ajax request.
Q62. What are various methods to make ajax request in jQuery?
Ans: Using below jQuery methods, you can make ajax calls.
load() : Load a piece of html into a container DOM
$.getJSON(): Load JSON with GET method.
$.getScript(): Load a JavaScript file.
$.get(): Use to make a GET call and play extensively with the response.
$.post(): Use to make a POST call and don't want to load the response to some container DOM.
$.ajax(): Use this to do something on XHR failures, or to specify ajax options (e.g. cache: true) on the fly.
Find out more here.
Q63. Is there any advantage of using $.ajax() for ajax call against $.get() or $.post()?
Ans: By using jQuery post()/ jQuery get(), you always trust the response from the server and you believe it is going to be successful all the time. Well, it is certainly not a good idea to trust the response. There may be n number of reason which may lead to failure of response.
Where jQuery.ajax() is jQuery's low-level AJAX implementation. $.get and $.post are higher-level abstractions that are often easier to understand and use, but don't offer as much functionality (such as error callbacks). Find out more here.
Q64. What are deferred and promise object in jQuery?
Ans: Deferred and promise are part of jQuery since version 1.5 and they help in handling asynchronous functions like Ajax. Find out more here.
Q65. Can we execute/run multiple Ajax request simultaneously in jQuery? If yes, then how?
Ans: Yes, it is possible to execute multiple Ajax request simultaneously or in parallel. Instead of waiting for first Ajax request to complete and then issue the second request is time consuming. The better approach to speed up things would be to execute multiple Ajax request simultaneously.
Using jQuery .when() method which provides a way to execute callback functions based on one or more objects, usually Deferred objects that represent asynchronous events. Find out more here.
Q66. Can you call C# code-behind method using jQuery? If yes, then how?
Ans: Yes. We can call C# code-behind function via $.ajax. But for do that it is compulsory to mark the method as WebMethod.
Q67. Which is the latest version of jQuery library?
Ans: The latest version (when this post is written) of jQuery is 1.10.2 or 2.0.3. jQuery 2.x has the same API as jQuery 1.x, but does not support Internet Explorer 6, 7, or 8.
Q68. Does jQuery 2.0 supports IE?
Ans: No. jQuery 2.0 has no support for IE 6, IE 7 and IE 8.
Q69. What are source maps in jQuery?
Ans: In case of jQuery, Source Map is nothing but mapping of minified version of jQuery against the un-minified version. Source map allows to debug minified version of jQuery library. Source map feature was release with jQuery 1.9. Find out more here.
Q70. How to use migrate jQuery plugin?
Ans: with release of 1.9 version of jQuery, many deprecated methods were discarded and they are no longer available. But there are many sites in production which are still using these deprecated features and it's not possible to replace them overnight.
So jQuery team provided with jQuery Migrate plugin that makes code written prior to 1.9 work with it.
So to use old/deprecated features, all you need to do is to provide reference of jQuery Migrate Plugin. Find out more here.
Q71. Is it possible to get value of multiple CSS properties in single statement?
Ans: Well, before jQuery 1.9 release it was not possible but one of the new feature of jQuery 1.9 was .css() multi-property getter.
var propCollection = $("#dvBox").css([ "width", "height", "backgroundColor" ]);
In this case, the propCollection will be an array and it will look something like this.
{
width: "100px",
height: "200px",
backgroundColor: "#FF00FF"
}
Q72. How do you stop the currently-running animation, remove all queued animations, and complete all animations for the matched elements?
Ans: It can be done via calling .stop([clearQueue ] [, jumpToEnd ]) method and by passing both the parameters as true.
Q73. What is finish method in jQuery?
Ans: The .finish() method stops all queued animations and places the element(s) in their final state. This method was introduced in jQuery 1.9.
Q74. What is the difference between calling stop(true,true) and finish method?
Ans: The .finish() method is similar to .stop(true, true) in that it clears the queue and the current animation jumps to its end value. It differs, however, in that .finish() also causes the CSS property of all queued animations to jump to their end values, as well.
Q75. Consider a scenario where things can be done easily with javascript, would you still prefer jQuery?
Ans: No. If things can be done easily via CSS or JavaScript then You should not think about jQuery. Remember, jQuery library always comes with xx kilobyte size and there is no point of wasting bandwidth.
Q76. Can we use protocol less URL while referencing jQuery from CDNs?
Ans: Yes. Below code is completely valid.
<script type='text/javascript' src='//ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js'></script>
Q77. What is the advantage of using protocol less URL while referencing jQuery from CDNs?
Ans: It is quite useful when you are moving from HTTP to HTTPS url. You need to make sure that correct protocol is used for referencing jQuery library as pages served via SSL should contain no references to content served through unencrypted connections.
"protocol-less" URL is the best way to reference third party content that’s available via both HTTP and HTTPS. When a URL’s protocol is omitted, the browser uses the underlying document’s protocol instead. Find out more here.
Q78. What is jQuery plugin and what is the advantage of using plugin?
Ans: A plug-in is piece of code written in a standard JavaScript file. These files provide useful jQuery methods which can be used along with jQuery library methods. jQuery plugins are quite useful as its piece of code which is already written by someone and re-usable, which saves your development time.
Q79. What is jQuery UI?
Ans: jQuery UI is a set of user interface interactions, effects, widgets, and themes built on top of the jQuery JavaScript Library that can be used to build interactive web applications.
Q80. What is the difference between jQuery and jQuery UI?
Ans: jQuery is the core library. jQueryUI is built on top of it. If you use jQueryUI, you must also include jQuery.
Note: If you have any questions to add to this list then please put it comments. We will be glad to add them in this list. We will be updating this list with new questions and share the updates on our Facebook or Twitter channel. If you are not following us then request you to please follow and stay updated.

CakePHP Interview Questions and Answers

2015-01-19T05:00:00.000-08:00

Here there are many questions and answers about How CakePHP Framework works? and basic questions related to CakePHP framework functionality.

Q-1What is CakePHP ?

Ans. CakePHP is a free, open-source, rapid development framework for PHP. It’s a foundational structure for programmers to create web applications. There is number of in built component like Ajax, RequestHandler, Session etc

Q-2 What are are drawbacks of cakephp.

Ans. The learning curve, and it loads full application before it starts your task. Its not recommended for small projects because of its resource heavy structure.

Q-3 What is MVC (model, view, and controller) in cakephp?

Ans. Model–view–controller (MVC) is an architectural pattern used in software engineering.

Model: Databases function exist in the model

View: Design parts written here

Controller: Business Login

Q-4 What is the name of Cakephp database configuration file name and its location?

Ans. Default file name is database.php.default.

Its located in “/app/config/database.php.defaut”

Q-5 What are component, helper and why are they used?

Ans. A component is an independent piece of code written for specific task that can be used(Eg Email, Ajax, RequestHandler and Session).

A helper is used for helping cakephp in rendering the data to be shown to user with views(Eg Form, HTML etc).

Q-6 What are commonly used components of cakephp?

Ans.

Security

Sessions

ACL(Access control lists)

Auth(Authentication)

Emails

RequestHandling

MVC architecture

Built-in validations

Caching

scaffolding

Q-7 What is default function and default controller of cakephp which is called automatically?

Ans. Default controller is indexController.php and Default function is index.

Q-8 How cakephp URL looks in address bar?

Ans. http://example.com/controller/action/param1/param2/param3

Q-9 Why cakephp have two vendor folder?

Ans. There is two vendor folder, one folder in root and another is in “app” folder

Q-10 List some database related functions in cakephp.

Ans. find, findAll , findAllBy , findBy , findNeighbours and query.

Q-11 List some of the features in Cakephp

Ans. Following are some feature of Cakephp.

MVC architecture

Built-in validations

Caching

scaffolding

Q-12 can you remember what is the directory structure when you download cakephp?

Ans. app/

o config/

o controllers/

o models/

o plugins/

o tmp/

o vendors/

o views/

o webroot/

* cake/

o config/

o docs/

o libs/

* vendors/

Q-13 List some of the features in Cake php.

Ans.

1. Compatible with versions 4 and 5 of PHP

2. MVC architecture

3. Built-in validations

4. Caching

5. scaffolding

Q-14 What is the naming convention in cakephp?

Ans. Table names are plural and lowercased,model names are singular and CamelCased: ModelName, model filenames are singular and underscored: model_name.php, controller names are plural and CamelCased with *Controller* appended: ControllerNamesController, controller filenames are plural and underscored with *controller* appended: controller_names_controller.php,

Q-15 How can we use ajax in cakephp?

Ans. By calling ajax helper and then using it in controller for rendering.

Q-16 What is a component,helper and why are they used, is there other way we can do same thing, what is better.

Ans. A component is an independent piece of code written for specific task that can be used by calling in controllers (example : email component), helper is used for helping cakephp in rendering the data to be shown to user with views, these only adds to modularity in code otherwise same coding can be implemented in conrollers.

Q-17 If you have to validate a registration module for a user, what all can be possible ways , which one is the best?

Ans. can be done on submission in controller, or using javascript/ajax while user is still filling the data. second option is better.

Q-18 How can you include a javascript menu throughout the site. Give steps.

Ans. By adding the javascript files in webroot and call them in default views if needed everywhere or just in the related veiws.

Q-19 What is a Component in cakephp?

Ans. Components are packages of logic that are shared between controllers. They are useful when a common logic or code is required between different controllers.

Q-20 What are commonly used components of cakephp?

Ans.

1. Security

2. Sessions

3. Access control lists

4. Emails

5. Cookies

6. Authentication

7. Request handling

(21) What is Cakephp?

CakePHP is a free, open-source, rapid development framework for PHP. It’s a foundational structure for programmers to create web applications. CakePHP goal is to enable developers to work in a structured and rapid manner–without loss of flexibility. CakePHP takes the monotony out of web development.

(22) When CakePHP was developed?

Cake php started at april 2005.When a Polish programmer Michal Tatarynowicz wrote a minimal version of a Rapid Application Framework in PHP, dubbing it Cake.Cake php version 1.0 released in May 2006. (source:http://en.wikipedia.org/wiki/CakePHP)

(23) What is the current stable version of CakePHP?

2.5.4 (at the time of writing this post) released on 2014-09-02.

(24) What is MVC in CakePHP?

Model view controller (MVC) is an architectural pattern used in software engineering.

Model: Database functions exist in the model

View: Design parts written here

Controller: Business Logic goes here

To understand in detail : http://www.php-dev-zone.com/2013/07/mvc-architecture-of-cakephp.html

(25) Server requirements for CakePHP.

Here are the requirements for setting up a server to run CakePHP:

An HTTP server (like Apache) with the following enabled: sessions, mod_rewrite (not absolutely necessary but preferred)

PHP 4.3.2 or greater. Yes, CakePHP works great in either PHP 4 or 5.

A database engine (right now, there is support for MySQL 4+, PostgreSQL and a wrapper for ADODB).

(26) How to install CakePHP?

step1: Go to cakephp.org and download the latest version of cakephp.

step2: Cakephp comes in a .zip file,so unzip it.

step3: Extract the files in the localhost in the desired folder (for example:cakephp).

step4: Open the browser and run the URL localhost/cakephp

step5: Just Follow the instructions display on the page.

(27) What is the folder structure of CakePHP?

cakephp/

app/

Config/

Console/

Controller/

Lib/

Locale/

Model/

Plugin/

Test/

tmp/

Vendor/

View/

webroot/

.htaccess

index.php

lib/

plugins/

vendors/

.htaccess/

index.php/

README.md/

(28) What is the name of Cakephp database configuration file name and its location?

Default file name is database.php.default.

Its located at "/app/config/database.php.default".To connect with database it should be renamed to database.php

(29) What is the first file that gets loaded when you run a application using cakephp?can you change that file?

bootstrap.php

yes it can be changed.Either through index.php , or through .htaccess

(30) What is the use of Security.salt and Security.cipherSeed in cakephp? How to change its default value?

- The Security.salt is used for generating hashes.we can change the default Security.salt value in /app/Config/core.php.

- The Security.cipherseed is used for encrypt/decrypt strings.We can change the default Security.cipherSeed value by editing /app/Config/core.php.

(31) What are controllers?

A controller is used to manage the logic for a part of your application. Most commonly, controllers are used to manage the logic for a single model. Controllers can include any number of methods which are usually referred to as actions. Actions are controller methods used to display views. An action is a single method of a controller.

(32) What is default function for a controller?

index() function

(33) Which function is executed before every action in the controller?

function beforeFilter()

(34) List some of the features in CakePHP

1. Compatible with versions 4 and 5 of PHP

2. MVC architecture

3. Built-in validations

4. Caching

5. Scaffolding

6. Access Control Lists and Authentication.

7.CSRF protection via Security Component.

(35) Using cakephp, what all are drawbacks.

it loads full application before it starts your task. Its not recommended for small projects because of its resource heavy structure.

(36) What is the naming convention in cakephp?

Table names are plural and lowercased,model names are singular and CamelCased: ModelName, model filenames are singular and underscored: model_name.php, controller names are plural and CamelCased with *Controller* appended: ControllerNamesController, controller filenames are plural and underscored with *controller* appended: controller_names_controller.php,

(37) What is Scaffolding in Cakephp?

Scaffolding is a technique that allows a developer to define and create a basic application that can create, retrieve, update and delete objects.

(38) How to add Scaffolding in your application?

To add scaffolding to your application,just add the $scaffold variable in the controller,

<?php

class PostsController extends AppController {

var $scaffold;

}

Assuming you’ve created Post model class file (in /app/Model/post.php), you’re ready to go. Visit http://example.com/posts to see your new scaffold.

(39) What is a Component in cakephp?

Components are packages of logic that are shared between controllers. They are useful when a common logic or code is required between different controllers.

(40) What are commonly used components of cakephp?

1. Security

2. Sessions

3. Access control lists

4. Emails

5. Cookies

6. Authentication

7. Request handling

8. Scaffolding

(41) What is a Helper?

Helpers in CakePHP are associated with Presentation layers of application.

Helpers mainly contain presentational logic which is availabel to share between many views, elements, or layouts

(42) What are commonly used helpers of cakephp?

FormHelper

HtmlHelper

JsHelper

CacheHelper

NumberHelper

Paginator

RSS

SessionHelper

TextHelper

TimeHelper

(43) What is a Behavior?

Behaviors in CakePHP are associated with Models.

Behaviors are used to change the way models behaves and enforcing model to act as something else.

(44) What is the difference between Component, Helper, Behavior?

Component is a Controller extension, Helpers are View extensions, Behavior is a Model Extension.

(45) What is a Element?

Element in cakephp are smaller and reusable bits of view code. Elements are usually rendered inside views.

(46) What is a layout?

Layout in cakephp are used to display the views that contain presentational code. In simple views are rendered inside a layout

(47) How to set layout in the controller?

var $layout = ‘layout_name’;

to overwrite for a specific action use below code in that action

$this->layout =”layout_name”;

(48) How to include helpers in controller ?

public $helpers = array(‘Form’, ‘Html’, ‘Js’, ‘Time’);

to in specific action use below code in that action

$this->helper[] =”helper_name”;

(49) How to include components in controller ?

public $components = array(‘Emails’, ‘ImageUploader’, ‘Sms’);

(50) How to write, read and delete the Session in cakephp?

$this->Session->write(‘Bird.Color’, ‘Black’);

$black = $this->Session->read(‘Bird.Color’);

$this->Session->delete(‘Bird’);

(51) What is the use of $this->set();

The set() method is used for creating a variable in the view file.Say for example if we write,

$this->set('posts',$posts); in controller fie, then the variable $posts will be available to use in the view template file for that action.

(52) What is the use of $this->set(compact());

Using $this->set(compact()) , we can pass multiple parameters to access into the view file.

For example,

$this->set(compact('posts','users','reports'));

Now all these variables will be available in respective view file.

(53) What are the advantages of each?which would you use and why?

An advantage with first case $this->set('posts', $posts); is that it allows two different names for the view file and controller file. For example, you could write something like $this->set('postData', $posts);. Now the variable name in the view file would be $postData.

The advantage with the second approach $this->set(compact()); is easier to write, and useful especially when we are setting several variables to the view.No need to add separate line for each variable as we have with $this->set();

For example,

$this->set(compact('posts','users','reports'));

(54) Is it possible to have Multiple validation Rules per Field in cakephp?

Yes its possible.

(55) What is wrong with the below validation rule?

'email' => array(

'rule' => array(

'rule' => 'notEmpty',

'message' => 'Please Enter Email address.'

'rule' => array(

'rule' => 'email',

'message' => 'Entered Email address is invalid.'

)

The problem is the first rule notEmpty will never be called because email rule will overwrite it.While using multiple validation rules for the same field you must keep the rule key "unique". In this case if we want to use multiple rules then, we can simple change the rule key names like,

'email' => array(

'rule1' => array(

'rule' => 'notEmpty',

'message' => 'Please Enter Email address.'

'rule2' => array(

'rule' => 'email',

'message' => 'Entered Email address is invalid.'

)

(56) What is the defference between required and notEmpty in cakephp?

To understand this question read this post:

http://www.php-dev-zone.com/2014/08/difference-between-required-and.html

(57) How to Get current URL in CakePHP?

To get current url in cakephp use,

echo Router::url($this->here, true);

This will give full URL with hostname.If you want to get relative path instead of full URL,then use the following code:

echo $this->here;

This will produce absolute URL excluding hostname i.e. /controller/abc/xyz/

(58) How can you make urls search engine friendly while using cakephp?

It's an automatic task that is done by cakephp.

(59) Can you list some database related functions in cakephp?

find, findAll , findAllBy , findBy , findNeighbours and query.

(60) Which methods are used to create and destroy model associations on the fly?

The bindModel() and unbindModel() Model methods are used to create and destroy model associations on the fly.

(61) What is the use of requestAction method?

The method requestAction is used to call a controller’s action from any location and returns data from the action.

(62) What is recursive in cakephp?

To understand this topic follow this post :

Recursive in cakephp

(63) How can we use ajax in cakephp?

By calling ajax helper and then using it in controller for rendering.

(64) What is habtm?

Has and belongs to many is a kind of associations that can be defined in models for retrieving associated data across different entities.

(65) How cakephp URL looks in address bar?

http://example.com/controller/action/param1/param2/param3

(66) How can you include a javascript menu throughout the site. Give steps.

By adding the javascript files in webroot and call them in default views if needed everywhere or just in the related veiws.

(67) Why cakephp have two vendor folder?what is the difference between two vendors folder available in cakephp?

There will be two vendor folders available in cakephp frame work.

one in ” app ” folder and one in root folder

The vendor folder in the app folder is used to place the third-party libraries which are application specific.

The vendor folder in the root folder is used to place the third-party libraries which are used for multiple applications.

(68) What is the default extension of view files in cakephp?can we change it?if yes then how?

default extension of view files is '.ctp'.

yes we can change it by writing public $ext = '.yourext'; in AppController.If you want to change it for particular controller then add it into that controller only.You can also change it for the specific action of the controller by putting it in that action of controller.

public $ext = '.yourext'; in AppController

- you can change all the views extentions.

public $ext = '.yourext'; in specific controller like, PostsController

- you can change all the views extentions of PostsController.

public $ext = '.yourext'; in specific controller action like, index()

- you can change the view extention of index.ctp

Note: You cannot specify multiple extensions, however it seems like there is a fall back to .ctp if no .php file is found.

(69) How can you set custom page title for the static page?

To set a custom page title, copy-paste following code anywhere in your static page (.ctp) file:

$this->set("title_for_layout", "My page title");

(70) How to display the schema of the model?

If you want to disply the schema of particular model then you just need to add the following single line of code.For example we have “Posts” Controller.

pr($this->Post->schema());

SEO Interview Questions 2014

2012-05-18T02:17:00.001-07:00

1. What Is SEO?

Search engine optimization (SEO) is the process of changing the position of a website or a web page in a search engine's search results (Organic or Natural results).

(or)

SEO stands for search engine optimization and is a part of internet marketing. SEO is a method by which the visibility of a website or a web page is increased on search engine.
Google, yahoo, bing

2. Types of SEO

Two Types of SEO are

    On Page Optimization

    Off Page Optimization

3. SEO Techniques

Two SEO Techniques are

     White Hat SEO

    Black Hat SEO ( Negative SEO )

4. What is On Page Optimization?

On-page optimization is one of the types of SEO that refers to factor that gives outcome to website or web page ranking on SERP ( Search Engine Results Page ). On-Page Optimization means controlling webpage by you or by your page coding.

Some of the examples are HTML Code, Meta Tags like Meta Title, Description, Content Quality, Keyword Density, Outbound Links, Image Alt tag etc.

5. What is Off Page Optimization?

Off Page Optimization is also one of the types of SEO that are not controlled by the page coding.

Examples of Off-page optimization Link building, Blog posting, Image Sharing, Document Sharing, Video Sharing, Info graphics submission, Increasing Page Rank and Page Authority, Article submission, Getting high quality links from relevant sites etc.

6. What is Page Rank or PR?

Page Rank is a rank that has been provided by Google for each and every Webpage. This Rank ranges from 0 to 10. This Page Rank is calculated by an Algorithm used by Google Web Search Engine. PR of a web page is based on the number of backlinks that received from other high PR webpage.

7. What is a Backlink?

Backlink means incoming links to a website or webpage. Inbound links are always better than outbound links. Those links are also known as incoming links, inlinks, inward links etc. Getting backlinks from high PR and relevant site is always good. Inlinks from .org, .edu sites would increase your website or webpage ranking on SERP. Do-follow links are better than No-follow links.

8. What are out bound Links?

An outbound-link (OBL) or outgoing link is a link from your website or webpage to another website or webpage.

9. What is a keyword?

Keyword is a word that is used for searching through Search Engines in order to get results related to your searched query.

10. What is Keyword Density?

Keyword density is the percentage density of a keyword or phrase available on a webpage compared to the total number of words on the page. It is one of the important ranking factors for search engines to display a webpage on the SERP. Providing junk keywords on a page would decrease the ranking of a webpage.

11. What is Anchor Text?

Anchor text is a clickable hyperlink that is also known as link text, link label and link title. The keyword contained in the anchor text would increase the ranking of a webpage that receives the incoming link.

12. What are organic results?

The page views come directly through SERP and not through any Off Page Optimization is known as organic results.

13. What is Googlebot?

Googlebot is the search bot software used by Google to index a webpage. Crawling, Caching and indexing of a webpage happen through this Googlebot by collecting details from that webpage.

14. What are Meta Tags?

There are several Meta tags used in HTML but the top four tags that are used for SEO are Meta Title, Meta Description, Meta Keywords and Robot tags.

15. What is Meta Title?

Title is the most important factors for a good SEO of a webpage. These tags should be located within head section. These tags should tell some useful information about that page. A good title tag should contain 60 characters. These titles would appear on the SERP for your website along with the Meta description of that page. Google won't penalize your page if it contains title with more than 60 characters and it skips the remaining characters. If a web page doesn't contain title tag means Google would select the H1 tag as title or it will provide the title by its own.
Always write title tag for the page and not for SEO, if you stuff keywords in you title then Google won't rank your webpage.

16. What is Meta Description?

A description tag should describe a webpage and it should contain keywords but don't stuff all the keywords. Meaningless description would affect your webpage. A description tag should contain 150 – 160 characters. If you provide meaningless or empty description, Google would take the description from the content available in that page.

17. What are Meta Keywords?

In early days Meta keywords are the least important tag for Search engine like Google. But it is an easy way to tell our important keywords to search engine. Meta keywords should contain less than 250 characters.
Now Google won't consider Meta keywords as one of the ranking factor.

18. What is White Hat Seo?

White Hat SEO is one of the SEO techniques that a Search engine always likes. Usage of SEO techniques, tricks and tactics by following search engine rules and regulations, algorithm and policies are known as White Hat SEO.

19. What is Black Hat Seo?

Black Hat SEO or Negative SEO is a common term for doing SEO Spamming Techniques. Usage of SEO by not following policies and regulations of search engine is called as black hat seo. Some of the black hat seo techniques are

    Providing Low Quality content or duplicate content on the page
    Getting backlinks from spammed or adult sites.
    Giving keyword stuffed content on the page with background color
    Getting too much backlinks from a single page with different anchor text that targets a single page of your website.
    Cloaking
    Google Bowling etc

20. On Page SEO Step 2 – Keyword in the URL
On Page SEO and to rank for your keyword when you are blogging and using your name in the domain name. I’m going to show you how it applies to your domain with your name in it. Remember to always put the keyword in the URL
For example: Use www.yourname.com/keyword insteadof www.yourname.com/2010/10/?p=210392.html

21. Difference between keyword & keyword phrase?

The keyword term is basically concerned with a one-word term, on the other hand a keyword phrase considered as employment of two or more word-combinations. Therefore, it is very confounded to get high ranking in account of one-word keyword term until the one-word keyword has little online competition. Therefore, this practice is not encouraged to employ. In order to drive more traffic and top ranking in SERP it is recommended to employ keyword phrase.

22. What is the difference between search engine marketing and Internet marketing?

Search Engine Marketing is specific to marketing your brand/service/products through search engines. It can be in the form of organic search results where landing pages are aimed for higher ranking, or in paid search results, where ads are aimed to display at maximum exposure for targeted keywords at minimal cost possible.

Internet marketing covers a broader range of channels. It includes search engine marketing, email marketing / EDM, social media, and so on.

23. How will you solve canonicalization issue or what is .htacess file?

.htacess file is used to solve the canonicalization issue of a website. It may happen that the home page of the site may take several urls like

http://www.seocutts.com/orhttp://www.seocutts.com/index.html or http://seocutts.com/ .

The search engines might treat these url as different and may divide the link juice gained by having various backlinks made with any of these 3 urls. The link juice gets divided between these three urls equally. .htacess file is created to have a single url of the home page so that the link juice is passed onto single url.

24. What is the difference between white hat and black hat?

White hat is what the search engines have stated as being within their guidelines for search engine optimization. Black hat is generally unethical tactics to have a page rank. It usually doesn't work for long and can get you penalized.

25. What is your favorite SEO website/blog, and why?
This is an open ended question. There were some that I were looking for but I was also hoping soemone would tell me a few that I didn't know about.
SeoMoz,
Analytics.Blogspot.com,
GoogleWebMasterCentral.Blogspot.com,
InsideSearch.Blogspot.com and
Search Engine Roundtable are a few good ones. There are actually a lot more.

26. What is on page and off page seo?

On page SEO are the things you can do within the website you own in order to help it rank for the keywords and phrases that you would like it to. Off page SEO are the things that you can do on other web sites towards those same goals.

27. What is the best way to maximize the frequency of crawling of your website by search engines?

Frequently adding new, original and quality content on the website.

28. I noticed that you don’t do a 301 redirect on your site from the non-www to the www version, Matt. Why not? Are you stupid in the head?

Actually, it’s on purpose. I noticed that several months ago but decided not to change it on my end or ask anyone at Google to fix it. I may add a 301 eventually, but for now it’s a helpful test case.

29. What is the difference between Indexing and Crawling?

1) When the Search Engines come to your website and read the data or find the data, this process is called crawling.

2) Whenever Search Engines come to your website, whichever page they crawl, they take a copy of that page with them and save it on their server. This process is done by the search engine is called Indexing

30. Is there a way we can tell Google that a particular webpage contains the Adult content?
Yes, we can do it by adding one of these two meta tags to that webpage
<meta name="rating" content="adult" /> OR
<meta name="rating" content="RTA-5042-1996-1400-1577-RTA" />

31. What is Pagination in SEO?

Pagination is the practice of dividing a piece of content into different pages while at the same time allowing Google to better understand the important pages to be indexed. Read the Google's advice on using the pagination.

32. What are top SEO ranking factors?

Quality of content on the webpage, quality and quantity of backlinks to the webpage, anchor text used in the backlinks, domain authority, social sharing metrics and some other traffic metrics like page CTR, bounce rate and average time on the webpage.

33. Google’s Quality Score and what role does it play in ranking?

While I do not expect Google’s textbook answer,, I am hoping the candidate understands the basic concept behind QS (clickthrough rate + other factors) and that QS is part of the Ad Rank formula where:

Ad Rank = CPC bid X Quality Score.

Their ability to explain Quality Score and Ad Rank to me in plain English is something I pay very close attention to.

Quality Score for Google and the search network is a dynamic metric assigned to each of your keywords. It’s calculated using a variety of factors and measures how relevant your keyword is to your ad group and to a user’s search query. The higher a keyword’s Quality Score, the lower its cost-per-clicks (CPCs) and the better its ad position.

34. How to achieve good CTR in PPC?

Here are few things that need to be kept in mind for CTR
■Target your ads to right audience
■Select correct keyword matching
■See that you target your ads by location and language
■Create different Ad Groups for different search phrases/keywords
■Calculate how much you can afford for the day
■test your ads on daily basis, change if you don`t get any response from users
■Give google users a good reason to click your ad

35. What is pay per click? Which internet marketing model does it follow?

‘Pay per click’ , also known as ‘cost per click’ is a form of internet advertising which is used for directing traffic to websites. In this advertisers pay the site owners or publishers for the ads being viewed or click. Pay per click introduces a simple strategy of marketing in which an advertiser pays the website for publishing his advertisement and getting people to view it by clicking it, the more the views are for the advertisement, better is the revenue generated by the website from advertisement. Generally ‘pay per click’ is used by advertisers on keyword phrases relevant to their target markets. Content sites generally charge a fixed amount per click rather than using a bidding system. ‘Pay per click’ advertisements are commonly displayed on websites and search engine results.‘Pay per click’ is an approach that differs from the ‘pay per impression’ methods used in television and newspaper advertising.

36. Where do you put your robots.txt?

a) Search for it in Google
b) In Webmaster Tools
c) The root directory of your domain or subdomain(s)
d) In the folder you want to disallow

37. Your site is flagged as having malware, but you can’t find the malware. What do you do?

a) Submit a reconsideration request
b) Post in the Google Webmaster Help Forum to ask for help
c) Tweet a complaint to @google
d) Abandon your domain name and start over again

38. “Unreachable robots.txt” in Webmaster Tools crawl errors means

a) You don’t have a robots.txt file
b) We couldn’t reach the robots.txt file on your server
c) Your robots.txt file disallows access to your robots.txt file
d) Your robots.txt file requires a password

39. You would like your site to be found for some keywords related to your content which are only found in images on the page. How do you do this?

a) Place the keywords in an image on the website
b) Use the “keywords” meta tag
c) Use the “description” meta tag
d) Use the “alt” attribute or include the keywords in your text
e) Place them in tiny text in the footer

40. All major search engines are case sensitive.
a.True
b.False

41. Which of the following file is created to give instructions to SE bots?

a. Index.html
b. Spiders.txt
c. sitemap.xml
d. Robots.txt
e. Searchbot.xml

42. What is the difference between 301 redirect & 302 redirect ?
The difference between a 301 and a 302 is that a 301 status code means that a page has permanently moved to a new location, while a 302 status code means that a page has temporarily moved to a new location.

_______________________________________________________________________________

If you have little bit of experience, here are the frequently asked questions for you:

1. What was your exact job profile in your previous company?
Provide a suitable explanation about your job profile which would include your job responsibilities and the amount of work you have handled so far.

2. How will you increase the Pagerank of a page?

By building more backlinks from authority sites and high page rank webpages.

3. How will you check the number of backlinks of your competitors site?

With the help of the link operator on Google and by using various external tools like Alexa, Backlink Watch , Open Site Explorer,Backlink finder etc.

4. What is the difference between Spiders, Robots and Crawlers?

A spider, also known as a robot or a crawler, is a program that follows, or "crawls", links throughout the Internet, grabbing content from sites and adding it to search engine indexes.

5. What is the difference between SEO and SEM?

SEO stands for Search Engine Optimization while SEM stands for Search Engine Marketing. SEO provides organic traffic to a website with the help of search engines while SEM involves the use of Google adwords and other paid channels of advertising.

6. Why does Google rank Wikipedia for so many topics?

Wikipedia is an established authority! As such, it is referenced by huge numbers of other documents with relevant text associated with links back to Wikipedia.

Some Most SEO Questions and Answers

Have look for some more SEO questions and Answers:-

1. What is the method to content optimization?
Answer:- There are so many way by which we can optimize our content. Here i will suggest some things which is necessary to know.

a) Keyword density in content
b) Keyword Proximity
c) Keyword Prominence
d) Keyword Proximity

2. Can you please suggest the type of keywords?

Ans: I will suggest you some most important type of keywords:-
a) Primary Keywords
b) Secondary Keywords
c) Branded Keywords
d) Non Branded Keywords
e) Seasonal Keywords

3. What is the difference between targeted page and Landing Page?

Ans:- Page which we have targeted to rank the page known a s targeted page and the page which has ranked called landing page.

4. Can you please suggest the meaning of Call to Action?

Ans:- There are so many things which we have used to increase the CTR of our page known as Call to action for more info you can contact me at kumarpdp.seo@gmail.com.com

5. Can you please tell the 5 most important on page factors?

Ans:- Hi as i think following are the most important factor for SEO.

1. Title
2. Description
3. Heading Tag
4. Image Optimization
5. Content Optimization

State	Description
0	The request is not initialized.
1	The request has been set up.
2	The request has been sent.
3	The request is in process.
4	The request is completed.

Technical FAQs for PHP and SEO Beginners

On This Day In History 16 November

What happened on November 16 in the history of India and the world?

Famous events, birth anniversaries, and death anniversaries today, November 16 in Indian and world history.

Historical events in Indian and world history on November 16

Famous birthdays on this day – November 16 in Indian history

Death anniversaries of famous people on this day – November 16

Top 38 SEO Interview Questions & Answers

Latest PHP Technical Interview Questions & Answers for Freshers

How to create PHP web service with JSON respond? For Android, Iphone or Web Application.

Mysql Query

Display Database Engines

Query to select book categories which start with Non-alphabets

Query to select DUPLICATE categories with duplicate count

Query to remove duplicate elements.

Perform operations on date

Differences between SESSION and COOKIE

$_GET

$_POST

$_REQUEST

$_FILES

$_SESSION

$_COOKIE

$_SERVER

$_ENV

SQL SELECT Statement

SQL Concat Function:

SQL Alias:

SQL Aggregate Functions:

SQL Scalar Functions:

SQL WHERE clause syntax

LIKE logical operator:

Ending Wildcard:

Single Character Wildcard:

Summary:

Order by clause:

What are DESC and ASC Keywords?

ASC/DESC basic syntax:

Conclusion on ORDER BY, DESC and ASC:

Sub-Queries Vs Joins!

Conclusion on SQL Sub-Queries:

Why should we use JOIN’s?

Types of SQL JOINs:

SQL INNER JOIN Keyword:

INNER JOIN Query Example:

SQL LEFT JOIN Keyword:

SQL RIGHT JOIN Keyword:

FULL OUTER JOIN query Example:

Difference between SQL JOIN and UNION:

Conclusion on SQL UNION Queries:

Using GROUP BY with Aggregate Functions:

1) SQL GROUP BY with SUM() function:

2) SQL GROUP BY with COUNT() function:

3) SQL GROUP BY with COUNT() and SUM() function:

5) SQL GROUP BY with WHERE clause:

6) SQL GROUP BY with HAVING clause:

Conclusion on SQL GROUP BY Clause:

Difference between MySQL delete and truncate table

Both the functions are used to Split a string. Explode is used to split a string using another string.

Both the functions are used to Split a string. However, Split is used to split a string using a regular expression. On the other hand, Explode is used to split a string using another string.

GET (HTTP)

POST (HTTP)

Difference between “include” and “require” in php

Program in C

What is AJAX?

Rich Internet Application Technology

AJAX is Based on Open Standards

AJAX - Technologies

How to get second-highest salary employees in a table

Latest jQuery Interview Questions & Answers

CakePHP Interview Questions and Answers

SEO Interview Questions 2014