PHP: Hypertext Preprocessor

How to execute a python script from an html button

2021-03-22T03:31:00.000-07:00

There are various ways to make it done, very simple technique with security peace in mind, here might help you

1. First you need to install Flask
pip install flask
in your command prompt, which is a python microframework, don't be afraid that you need to have another prior knowledge to learn that, it's really simple and just a few line of code. If you wish you learn Flask quickly for complete novice here is the tutorial that I also learn from Flask Tutorial for beginner (YouTube)

2.Create a new folder
- 1st file will be server.py

from flask import Flask, render_template
app = Flask(__name__)

@app.route('/')
def index():
  return render_template('index.html')

@app.route('/my-link/')
def my_link():
  print ('I got clicked!')

  return 'Click.'

if __name__ == '__main__':
  app.run(debug=True)

-2nd create another subfolder inside previous folder and name it as templates file will be your html file
index.html

<!doctype html>
<head><title>Test</title> 
    <meta charset=utf-8> </head>
    <body>
        <h1>My Website</h1>
        <form action="/my-link/">
            <input type="submit" value="Click me" />
        </form>
        
        <button> <a href="/my-link/">Click me</a></button>

    </body>
3.. To run, open command prompt to the New folder directory, type python server.py to run the script, then go to browser type localhost:5000, then you will see button. You can click and route to destination script file you created.

Generate data format from current date to x months

2020-10-08T03:35:00.006-07:00

/**

 * Generate data format from current date to x months
 *
 * @param $months
 *
 * @return DateTime|string
 *
 * @throws Exception
 */
function generateDateByMonths($months)
{
    $date = '';
    $time = '23:59:59';
    if(is_numeric($months) && $months > 0) {
        $date = new DateTime('now');
        $date->modify('+'.$months.' month'); // or you can use '-2 months' for deduct
        $date = $date->format('Y-m-d');
    }
    return $date . ' ' . $time;
}

JavaScript: remove duplicate in multidimensional array by using specific key

2020-03-03T05:36:00.002-08:00

JavaScript finding intersection values from the 2 arrays

2020-03-03T05:33:00.002-08:00

function arrayIntersection(ar1, ar2) {
return ar1.filter(function(n) {
return ar2.indexOf(n) !== -1;
});
}

JavaScript function to remove duplicates in single dimension array

2020-03-03T05:31:00.001-08:00

function removeDuplicatesInSingleDimensionArray(array) {
return array.filter((a, b) => array.indexOf(a) === b)
};

Tips To Improve JavaScript Performance

2019-02-02T04:48:00.000-08:00

Tip #1 – Evaluate Local Variables

(http://blogs.msdn.com/b/ie/archive/2006/08/28/728654.aspx)

Primarily, specific to IE, because local variables are found based on the most to the least specific scope and can pass through multiple levels of scope, the look-ups can result in generic queries. When defining the function scope, within a local variable without a preceding var declaration, it is important to precede each variable with var in order to define the current scope in order to prevent the look-up and to speed up the code.

Tip #2 – Create shortcut codes to speed up coding

For useful codes that are constantly being used, speeding up the coding process can be achieved by creating shortcuts for longer codes, for example, document.getElementById. By creating a shortcut, longer scripts will not take as long to code and will save time in the overall process.

Tip #3 –Manipulate element fragments before adding them to DOM

(http://www.jquery4u.com/dom-modification/improve-javascript-performance)

Before placing the elements to the DOM, ensure that all tweaks have been performed in order to improve JavaScript performance. This will eliminate the need to set aside Prepend or Append jQuery APIs.

Tip #4 – Save bytes by using Minification

(http://sixrevisions.com/web-development/10-ways-to-improve-your-web-page-performance)

Reduce the file size of your JavaScript documents by removing characters (tabs, source code documents, spaces etc.) without changing the functionality of the file.

There are a number of minification tools that can assist in this process, and have the ability to reverse the minification. Minification is the process of removing all unnecessary characters from source code, without changing its functionality.

Tip #5 –Don’t use nested loops if not required

Avoid unwanted loops, such as for/while, in order to keep the JavaScript linear and to prevent from having to go through thousands of objects. Unwanted loops can cause the browser to work harder to process the codes and can slow down the process.

Tip #6 – Cache objects to increase performance

Many times, scripts will be repeatedly used to access a certain object. By storing a repeated access object inside a user defined variable, as well as using a variable in subsequent references to that object, performance improvement can be achieved immediately.

Tip #7 – Use a .js file to cache scripts

(http://www.javascriptkit.com/javatutors/efficientjs.shtml)

By using this technique, increased performance can be achieved because it allows the browser to load the script once and will only recall it from cache should the page be reloaded or revisited.

Tip #8 – Place JavaScript at the bottom of the page

Placing the scripts as low as possible in the page will increase the rendering progress, and also increase download parallelization. The result is that the page will seem to load faster, and in some cases it can also save on the total amount of code needed.

Tip #9 – Use jQuery as a framework

Used for the scripting of HTML, jQuery is an easy to use JavaScript library that can help to speed up any website. jQuery provides a large number of plug-ins that can quickly be used, by even novice programmers.

Tip #10 – Compress your files with GZip

(http://devmoose.com/coding/10-ways-to-instantly-speed-up-your-website)

GZip can reduce a JavaScript file considerably, saving bandwidth, and accelerate the response time. JavaScript files can be very large, and without compression, it can bog down any website. Smaller files provide a faster and more satisfying web experience.

Tip #11- Don’t use “With” keyword

(http://blogs.msdn.com/b/ie/archive/2006/08/28/728654.aspx)

The “With” keyword is considered a black-sheep because it suffers from several flaws that can be very frustrating. Although it makes the process of working with local properties simpler, “With” can make looking up variables in other scopes more expensive.

Tip #12 – Minimize requests for HTTP

(http://www.websiteoptimization.com/speed/tweak/http)

Minimize HTTP requests to render pages by combining external files and including JavaScript directly within XHTML pages. Each time a unique HTTP takes a trip to a server, the result is a large number of delays.

Tip #13 – Implement Event Delegation

With Event Delegation, it becomes easier to use a single event handler to manage a type of event for the entire page. Without using Event Delegation, large web applications can grind to a halt because of too many event handlers. Benefits of Event Delegation include; less functionality to manage, fewer ties between code and DOM, and less memory required to process.

Tip #14 – Don’t use the same script twice

(http://www.abhishekbharadwaj.com/2010/12/speed-up-your-website-avoid-duplicate-scripts)

Duplicate scripts will have a significant impact on performance. Duplicate scripts will create unnecessary requests on HTTP, especially in the IE browser. Using a SCRIPT tag, in an HTML page, will help to avoid accidentally duplicating scripts.

Tip #15 – Remove Double Dollar $$

(http://www.mellowmorning.com/2008/05/18/javascript-optimization-high-performance-js-apps)

Using “double dollar $$” function is not necessarily needed, when it comes to improving the speed of a website.

Tip #16 – Creating reference variables

(http://mondaybynoon.com/2009/04/27/a-couple-of-quick-tips-for-javascript-optimization)

When working with a specific node repeatedly, it is best to define a variable with that particular note, instead of switching to it repeatedly. This is not a significant enhancement but it can have a bigger impact on a large scale.

Tip #17 – Increase speed of Object Detection

(http://dean.edwards.name/weblog/2005/12/js-tip1)

A more efficient method to using Object Detection is to use a code created dynamically based off of object detection, rather than performing object detection inside of a function.

Tip #18 – Write effective Loops

(http://robertnyman.com/2008/04/11/javascript-loop-performance)

Depending on the browser, the method used to write Loops can have a great effect on the performance of a site. Improper writing of loops can slow down pages with lots of queries and running a number of loops in parallel.

Tip #19 – Shorten Scope Chains

Global scopes can be slow, because each time a function executes, it cause a temporary calling scope to be created. JavaScript searchers for the first item in the scope chain, and if it doesn’t find the variable, it swells up the chain until it hits the global object.

Tip #20 – Index directly to NodeLists

NodeLists are live and can take up a lot of memory, as they are updated when an underlying document changes. Its quicker to index directly into a list, as a browser will not need to create a node list object.

Tip #21 – Don’t use ‘eval’

Although the “eval” function is a good method to run arbitrary code, each string that is passed to the eval function has to be parsed and executed on-the-fly. This cost has to be paid every time the execution reaches an eval function call.

Tip #22 – Use Function Inlining

(https://dl.acm.org/citation.cfm?id=844097)

Function Inlining helps to eliminate call costs, and replaces a function call with the body of the called function. In JavaScript, performing a function call is an expensive operation because it takes several preparatory steps to perform: allocating space for parameters, copying the parameters, and resolving the function name.

Tip #23 – Implement Common Sub-expression Elimination (CSE)

(http://sunilkumarn.wordpress.com/2010/10/19/common-subexpression-elimination-cse)

Common sub-expression elimination (CSE) is a performance-targeted compiler optimization technique that searches for instances of identical expressions and replaces them with a single variable holding the computed value. You can expect that using a single local variable for a common sub-expression will always be faster than leaving the code unchanged.

Tip #24 – Build DOM node and all its sub-nodes offline

When adding complex content such as tables to a site, performance is improved by adding complex sub-trees offline.

Tip #25 – Try not to use global variables

Because the scripting engine needs to look through the scope, when referencing global variables from within function or another scope, the variable will be destroyed when the local scope is lost. If variables in global scope cannot persist through the lifetime of the script, the performance will be improved.

Tip #26 – Use primitive functions operations vs. function calls

Improved speed can be achieved in performance critical loops and functions by using equivalent primitive functions instead of function calls.

Tip #27 – Don’t retain alive references of other documents

(http://dev.opera.com/articles/view/efficient-javascript/?page=4#docreferences)

By not retaining alive references of other documents after the script has finished with them, faster performance will be achieved. This is because any references to those objects from that document are not to be kept in its entire DOM tree, and the scripting environment will not be kept alive in RAM. Thus the document itself is no longer loaded.

Tip #28 – Use XMLHttpRequest

(http://dev.opera.com/articles/view/efficient-javascript/?page=4#docreferences)

XMLHttpRequest helps to reduce the amount of content coming from the server, and avoids the performance impact of destroying and recreating the scripting environment in between page loads. Its is important to ensure that XMLHttpRequest is supported, or otherwise it can lead to problems and confusion.

Tip #29 – Avoid using try-catch-finally

(http://dev.opera.com/articles/view/efficient-javascript/?page=2)

Whenever the catch clause is executed, where the caught exception object is assigned to a variable, “try-catch-finally” creates a new variable in the current scope at runtime. A number of browsers do not handle this process efficiently because the variable is created and destroyed at runtime. Avoid it!

Tip #30 – Don’t misuse for-in

(http://dev.opera.com/articles/view/efficient-javascript/?page=2)

Because the “for-in” loop requires the script engine to build a list of all the enumerable properties, coding inside for loop does not modify the array. It iterates pre-compute the length of the array into a variable len inside for loop scope.

Php isset

2012-06-12T04:39:00.001-07:00

isset

(PHP 4, PHP 5)

isset — Determine if a variable is set and is not NULL

Description

bool isset ( mixed $var [, mixed $... ] )

Determine if a variable is set and is not NULL.

If a variable has been unset with unset(), it will no longer be set. isset() will return FALSE if testing a variable that has been set to NULL. Also note that a NULL byte ("\0") is not equivalent to the PHP NULL constant.

If multiple parameters are supplied then isset() will return TRUE only if all of the parameters are set. Evaluation goes from left to right and stops as soon as an unset variable is encountered.

Report a bug

Parameters

var: The variable to be checked.
...: Another variable ...

Report a bug

Return Values

Returns TRUE if var exists and has value other than NULL, FALSE otherwise.

Report a bug

Changelog

Version	Description
5.4.0	Checking non-numeric offsets of strings now returns `FALSE`.

Example #1 isset() Examples


<?php

$var = '';
// This will evaluate to TRUE so the text will be printed.if (isset($var)) {
    echo "This var is set so I will print.";
}
// In the next examples we'll use var_dump to output
// the return value of isset().
$a = "test";$b = "anothertest";
var_dump(isset($a));      // TRUEvar_dump(isset($a, $b)); // TRUE
unset ($a);
var_dump(isset($a));     // FALSEvar_dump(isset($a, $b)); // FALSE
$foo = NULL;var_dump(isset($foo));   // FALSE
?>





This also work for elements in arrays:


    





<?php

$a = array ('test' => 1, 'hello' => NULL, 'pie' => array('a' => 'apple'));
var_dump(isset($a['test']));            // TRUEvar_dump(isset($a['foo']));             // FALSEvar_dump(isset($a['hello']));           // FALSE

// The key 'hello' equals NULL so is considered unset
// If you want to check for NULL key values then try: var_dump(array_key_exists('hello', $a)); // TRUE

// Checking deeper array valuesvar_dump(isset($a['pie']['a']));        // TRUEvar_dump(isset($a['pie']['b']));        // FALSEvar_dump(isset($a['cake']['a']['b']));  // FALSE
?>

Example #2 isset() on String Offsets

PHP 5.4 changes how isset() behaves when passed string offsets.


<?php
$expected_array_got_string = 'somestring';var_dump(isset($expected_array_got_string['some_key']));var_dump(isset($expected_array_got_string[0]));var_dump(isset($expected_array_got_string['0']));var_dump(isset($expected_array_got_string[0.5]));var_dump(isset($expected_array_got_string['0.5']));var_dump(isset($expected_array_got_string['0 Mostel']));?>

Output of the above example in PHP 5.3:

bool(true)
bool(true)
bool(true)
bool(true)
bool(true)
bool(true)

Output of the above example in PHP 5.4:

bool(false)
bool(true)
bool(true)
bool(true)
bool(false)
bool(false)

Linux interview questions 3

2012-05-04T06:35:00.000-07:00

What are the process states in Linux?

Process states in Linux:

Running: Process is either running or ready to run

Interruptible: a Blocked state of a process and waiting for an event or signal from another process

Uninterruptible:- a blocked state. Process waits for a hardware condition and cannot handle any signal

Stopped: Process is stopped or halted and can be restarted by some other process

Zombie: process terminated, but information is still there in the process table.

What is a zombie?

Zombie is a process state when the child dies before the parent process. In this case the structural information of the process is still in the process table. Since this process is not alive, it cannot react to signals. Zombie state can finish when the parent dies. All resources of the zombie state process are cleared by the kernel

Explain each system calls used for process management in linux.

System calls used for Process management:

Fork () :- Used to create a new process

Exec() :- Execute a new program

Wait():- wait until the process finishes execution

Exit():- Exit from the process

Getpid():- get the unique process id of the process

Getppid():- get the parent process unique id

Nice():- to bias the existing property of process

Linux interview questions 2

2012-05-04T06:33:00.000-07:00

What does nslookup do? Explain its two modes.

Nslookup is used to find details related to a Domain name server. Details like IP addresses of a machine, MX records, servers etc. It sends a domain name query packet to the corresponding DNS.

Nslookup has two modes. Interactive and non interactive. Interactive mode allows the user to interact by querying information about different hosts and domains.

Non interactive mode is used to fetch information about the specified host or domain.

Interactive mode:

Nslookup [options] [server]

What is Bash Shell?

Bash is a free shell for UNIX. It is the default shell for most UNIX systems. It has a combination of the C and Korn shell features. Bash shell is not portable. any Bash-specific feature will not function on a system using the Bourne shell or one of its replacements, unless bash is installed as a secondary shell and the script begins with #!/bin/bash. It supports regular and expressions. When bash script starts, it executes commands of different scripts.

Explain Some Network-Monitoring Tools in Linux: ping, traceroute, tcpdump, ntop

Network monitoring tools are used to monitor the network, systems present on the network, traffic etc.

Ping: Ping command is used to check if the system is in the network or not. To check if the host is operating.

e.g. ping ip_address

When the command is executed, it returns a detailed summary of the host. Packets sent, received, lost by estimating the round trip time.

Traceroute : the command is used to trace the path taken by the packet across a network. Tracing the path here means finding out the hosts visited by the packet to reach its destination. This information is useful in debugging. Roundtrip time in ms is shown for every visit to a host.

Tcpdump: commonly used to monitor network traffic. Tcdump captures and displays packet headers and matching them against criteria or all. It interprets Boolean operators and accepts host names, ip address, network names as arguments.

Ntop : Network top shows the network usage. It displays summary of network usage by machines on the network in a format as of UNIX top utility. It can also be run in web mode, which allows the display to be browsed with a web browser. It can display network traffic statistics, identify host etc. Interfaces are available to view such information.

Explain file system of linux. The root "/" filesystem, /usr filesystem, /var filesystem, /home filesystem, /proc filesystem.

Root "/" file system: The kernel needs a root file system to mount at start up. The root file system is generally small and should not be changed often as it may interrupt in booting. The root directory usually does not have the critical files. Instead sub directories are created. E.g. /bin (commands needed during bootup), /etc (config files) , /lib(shared libraries).

/usr filesystem : this file system is generally large as it contains the executable files to be shared amongst different machines. Files are usually the ones installed while installing Linux. This makes it possible to update the system from a new version of the distribution, or even a completely new distribution, without having to install all programs again. Sub directories include /bin, /include, /lib, /local (for local executables)

/var filesystem : this file system is specific to local systems. It is called as var because the data keeps changing. The sub directories include /cache/man (A cache for man pages), /games (any variable data belong to games), /lib (files that change), /log (log from different programs), /tmp (for temporary files)

/home filesystem: - this file system differs from host to host. User specific configuration files for applications are stored in the user's home directory in a file. UNIX creates directories for all users directory. E.g /home/my_name. Once the user is logged in ; he is placed in his home directory.

/proc filesystem :  this file system does  not exist on the hard disk. It is created by the kernel in its memory to provide information about the system. This information is usually about the processes. Contains a hierarchy of special files which represent the current state of the kernel .Few of the Directories include /1 (directory with information about process num 1, where 1 is the identification number), /cpuinfo (information about cpu), /devices (information about devices installed), /filesystem (file systems configured), /net (information about network protocols), /mem (memory usage)

Linux interview questions 1

2012-05-04T06:30:00.000-07:00

What is Kernel? Explain the task it performs.

Kernel is used in UNIX like systems and is considered to be the heart of the operating system. It is responsible for communication between hardware and software components. It is primarily used for managing the systems resources as well.

Kernel Activities:

The Kernel task manager allows tasks to run concurrently.

Managing the computer resources: Kernel allows the other programs to run and use the resources

Resources include i/o devices, CPU, memory.

Kernel is responsible for Process management. It allows multiple processes to run simultaneously allowing user to multitask.

Kernel has an access to the systems memory and allows the processes to access the memory when required.

Processes may also need to access the devices attached to the system. Kernel assists the processes in doing so.

For the processes to access and make use of these services, system calls are used.

What is Linux Shell? What is Shell Script?

Linux shell is a user interface used for executing the commands. Shell is a program the user uses for executing the commands. In UNIX, any program can be the users shell. Shell categories in Linux are:

Bourne shell compatible, C shell compatible, nontraditional, and historical

A shell script, as the name suggests, is a script written for the shell. Script here means a programming language used to control the application. The shell script allows different commands entered in the shell to be executed. Shell script is easy to debug, quicker as compared to writing big programs. However the execution speed is slow because it launches a new process for every shell command executed. Examples of commands are cp, cn, cd.

What are Pipes? Explain uses of pipes.

A pipe is a chain of processes so that output of one process (stdout) is fed an input (stdin) to another. UNIX shell has a special syntax for creation of pipelines. The commands are written in sequence separated by |. Different filters are used for Pipes like AWK, GREP.

e.g. sort file | lpr ( sort the file and send it to printer)

Uses of Pipe

Several powerful functions can be in a single statement

Streams of processes can be redirected to user specified locations using >

Explain trap command; shift Command, getopts command of linux.

Trap command: controls the action to be taken by the shell when a signal is received.

Trap [OPTIONS] [ [arg] signspec..]

Arg is the action to be taken or executed on receiving a signal specified in signspec.

e.g. trap “rm $FILE; exit” // exit (signal) and remove file (action)

Shift Command: Using shift command, command line arguments can be accessed. The command causes the positional parameters shift to the left. Shift [n] where n defaults to 1. It is useful when several parameters need to be tested.

Getopts command: this command is used to parse arguments passed. It examines the next command line argument and determines whether it is a valid option

Getopts {optstring} {variable1}. Here, optsring contains letters to be recognized if a letter is followed by a colon, an argument should be specified. E.g (whether the argument begins with a minus sign and is followed by any single letter contained inside options ) If not, diagnostic messages are shown. It is usually executed inside a loop.

What Stateless Linux server? What feature it offers?

A stateless Linux server is a centralized server in which no state exists on the single workstations. There may be scenarios when a state of a partilcuar system is meaningful (A snap shot is taken then) and the user wants all the other machines to be in that state. This is where the stateless Linux server comes into picture.

Features:

It stores the prototypes of every machine

It stores snapshots taken for those systems

It stores home directories for those systems

Uses LDAP containing information of all systems to assist in finding out which snapshot (of state) should be running on which system.

PhpMyAdmin Tutorial 6

2012-05-03T06:06:00.000-07:00

Retrieving Data with SELECT

Retrieving information from our tables is probably the operation we do most of the times. This is the way to get answers to questions like �what are the cities with a population over a certain number?�.

In fact, we previously did a SELECT when we clicked on the Browse link for table cities. This generated a simple form of the SELECT statement:

SELECT * FROM `cities` LIMIT 0,30;

Here, the asterisk means �all the columns�. We add FROM and the name of the table which we want to query. The LIMIT 0,30 means to start at row number 0 (the first one), and select a maximum of 30 rows.

Let's try a Search to see more options for the SELECT. We go to the Search sub-page for table cities, and we choose only some columns we need:

Then at the bottom of the page, we choose to display by the result by population in descending order:

Executing the search generates the following query:

SELECT `city_name` , `population`
FROM `cities`
WHERE 1
ORDER BY `population` DESC LIMIT 0,30

We see that the asterisk has been replaced by a comma-separated list of columns. A condition WHERE 1 has been added by phpMyAdmin, this is a condition which is always true and selects all rows. We will see in a moment that we can replace it with some other condition. Also, the clause ORDER BY appears, followed by the column on which we want to sort results, and the keyword DESC for descending order (we could also use ASC for ascending).

Conditions

To easily add a condition, on the results page we can click on SQL-query: Edit, which brings the Query window popup. We add a condition on the country:

SELECT `city_name` , `population`

FROM `cities`

WHERE country_code = 'zh'

ORDER BY `population` DESC

which displays all cities located in China (ok, we were a bit lazy with data entry, but you get the picture).

Conditions can be expressed using a rich array of operators and functions. Here are two examples:

Finding the Canadian cities with a population over 100000:

WHERE population > 100000 AND country_code = 'ca'

Finding the cities whose name starts with �A�:

WHERE city_name like 'A%'

Aggregate functions

Summary information may be generated by grouping on a specific column. Here we ask the average city population per country:

SELECT country_code, AVG(population)

FROM cities

GROUP BY country_code

Other possible aggregate functions are MIN(), MAX(), SUM() and COUNT(), which compute respectively the minimum value, maximum value, sum of values, and number of values. For example, we could get the number of cities per country with:

SELECT country_code, count(city_name)

FROM cities

GROUP BY country_code

Joins

Normally, a relational database involves many tables, linked on common keys. We may need at times to run queries on more than one table. Linking, or joining, tables can be done using different techniques; we will focus on a simple method involving key comparison.

In the following query, the FROM clause contains a comma-separated list of tables. In the columns list, we use the table name and a dot as a prefix before each column name (not strictly necessary if each column name is only present in one table).

SELECT cities.city_name, cities.population, countries.country_name
FROM cities, countries
WHERE cities.country_code = countries.country_code LIMIT 0,30

Conclusion

The SQL language has much more to it than the basic statements that we have covered here. However, this article has covered the basics of SQL and how to use the phpMyAdmin tool to advance your knowledge of SQL.

<<< PREVIOUS Will come.....

PhpMyAdmin Tutorial 5

2012-05-03T06:05:00.000-07:00

Data modification

In this section, we will learn the basic syntax for the INSERT, UPDATE, DELETE, and SELECT statements.

Adding Data with INSERT

Let's first examine the INSERT statement, by looking at the code phpMyAdmin generates when we do an Insert operation. We bring up the Insert sub-page, in Table view for the countries table, and we enter data about a country:

When we click Go, the data is inserted and phpMyAdmin shows us the INSERT statement used:

INSERT INTO `countries` ( `country_code` , `country_name` )
VALUES ('ca', 'Canada');

After the INSERT INTO part, we have the table name. In MySQL, we can enclose table names and column names within backticks, in case there are special characters in them, like reserved words or accented characters. Then we open a first set of brackets, listing the columns in which we want to insert, separated by commas. The reserved word VALUES follows, then the last set of brackets enclosing the values, in the same order as the columns list. If the values have a character data type, we have to enclose them within quotes.

We can now insert a city.

INSERT INTO `cities` ( `id` , `city_name` , `latitude` , `longitude` , `population` , `country_code` )
VALUES ('', 'Sherbrooke', '45 23 59.00', '-71 46 11.00', 125000, 'ca');

Here, we put an empty value for id, because this column's auto-increment attribute will provide a value. We also see that the population value, being numeric, does not need to be surrounded by quotes.

Let's end this section by inserting some data for another country and city, which we will need later.

INSERT INTO `countries` ( `country_code` , `country_name` )
VALUES ('zh', 'China');

INSERT INTO `cities` ( `id` , `city_name` , `latitude` , `longitude` , `population` , `country_code` )
VALUES ('', 'Shanghai', '31 13 58.00', '121 26 59.99', 11000000, 'zh');

Updating Data with UPDATE

We first click on Browse for table cities, displayed our single row of data.

By clicking on the small pencil-shaped icon (or Edit link), we go to the Edit panel for this row. We decide to change the population value to 130000. After a click on Save, phpMyAdmin shows the following statement:

UPDATE `cities` SET `population` = '130000' WHERE `id` = '1' LIMIT 1 ;

Here we have the UPDATE keyword, followed by the table name. The SET keyword introduces the list of modifications (here only the population), which follows the format column = new value.

We now see the condition WHERE `id` = '1', which uses the primary key information to limit the change to only this row, i.e. only this city.

The limit 1 part is a safeguard added by phpMyAdmin, in case there would be no primary key defined, to avoid doing the change to more than one row.

More than one column can be changed in a single UPDATE operation:

UPDATE `cities` SET `city_name` = 'Sherbrooke, Qu�bec',
`population` = '130001' WHERE `id` = '1' LIMIT 1 ;

Deleting Data with DELETE

In Browse mode on table cities, clicking on the small red trash-can icon (or Delete link) brings up a dialog to confirm the execution of the following statement:

DELETE FROM `cities` WHERE `id` = '1' LIMIT 1 ;

The syntax is simple, involving just the table name, and the condition to apply for the delete operation.

Omitting the WHERE condition in an UPDATE or DELETE operation is perfectly legal in SQL, but then the operation takes place on every rows of the table!

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PhpMyAdmin Tutorial 4

2012-05-03T06:03:00.000-07:00

Learning SQL Using phpMyAdmin

What is SQL?

Structured Query Language is a non-procedural language used to define, manipulate and retrieve data. It was developed by IBM (System/R project) in 1974-1979. The American National Standards Institute (ANSI) published in 1986 the first official standard of the language (later revised in 1989, 1992 and 1999), and since then, the industry has widely adopted SQL as the relational database language. Virtually every database system nowadays is interfaced through SQL.

The specific data architecture addressed by SQL is called the relational architecture. The various pieces of data (columns) are grouped into tables contained in databases, and we retrieve data using relations expressed between the tables.

In this article, we will use MySQL, a popular open-source implementation of SQL that is deployed by most Web host providers.

Toolkit for this guide

To be able to do the exercises in this guide, you will need an access to a MySQL server. Your interface to MySQL will be phpMyAdmin, a PHP application running on a PHP-enabled Web server.

Creating Sample Tables

We will use a geographical information system as an example. We decide that we need information about cities and countries, so we design two tables, which will be part of a database called geodb (although any database name would do). To create the tables, we can use phpMyAdmin's Structure sub-page inDatabase view, or we can use the SQL query box to enter the appropriate statement:

The table creation is accomplished with the CREATE TABLE statement, in which we give the new table's name. The statement begins with CREATE TABLE, followed by the table name. Then, enclosed in brackets, we put the list of columns, and information about the keys. Each column is assigned a name, data type, the NULL or NOT NULL attribute (here, NOT NULL means the column cannot have a NULL value) and a default value, if appropriate.

CREATE TABLE cities (

id int(11) NOT NULL auto_increment,

city_name varchar(50) NOT NULL default '',

latitude varchar(15) NOT NULL default '',

longitude varchar(15) NOT NULL default '',

population int(11) NOT NULL default '0',

country_code char(2) NOT NULL default '',

PRIMARY KEY (id)

) TYPE=MyISAM AUTO_INCREMENT=1 ;

The id column is our primary key, a column which uniquely identifies each city. Its data type is INT (an integer number), and MySQL will assign unique numbers to it, thanks to the auto_increment attribute. Note that we cannot use the city name as a primary key, as some city names are not unique in the world. We also use an integer for the population data.

The other columns use character (CHAR) or variable character (VARCHAR) data types. When we know the exact length of data, it's better to use CHAR, specifying the length of the column as in CHAR(2). Otherwise we use a variable character data type, which will take only the space needed by each piece of data, and we specify the maximum length, as in VARCHAR(15).

After the columns list, we have some table-specific information, like its type, and the first value for the auto-increment column. SQL statements end with a semi-colon.

Having created our cities table, we do the same operation, this time for the countries table.

CREATE TABLE countries (

country_code char(2) NOT NULL default '',

country_name varchar(100) NOT NULL default ''

) TYPE=MyISAM;

We notice that the country_code column is present in both tables. This shows the relational principle: the country_code in cities refers to the same column incountries. This way, we save on space, having each country name only once in our database.

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PhpMyAdmin Tutorial 3

2012-05-03T06:00:00.000-07:00

Inputting data into the table.

Click the tab labeled "Insert" - and another window should appear, like this.

Now type in the details for each of the fields for this record. The "id" column was set to automatically increment so you do not need to enter a number.

Note - if you ever get lost with phpMyAdmin navigation click "Home" in the left hand nav bar and start again.

Now click Save and the record is saved to the people table.
The previous window reappears with the SQL command for the insert. You can keep adding recordsby re-selecting Insert".
For multiple records, you can select the "Insert another new row" radio button on the input form.

When you've finished entering several records into the table, you can check them by clicking on the Browse tab. You can click on individual records for editing or deleting.

You can use the Select tab to refine your display when your database starts grows to many pages of records.

Backup your data

You "don't know what you've got 'til its gone"!

- Click on your database name in the left hand navigation bar

- Click on EXPORT (top tab)
- Highlight the table/s you want to back up
- Select STRUCTURE and DATA radio button

- Select "Enclose table and field names with backquotes"
- Select "Save as file" and "zipped" check boxes
- Click "Go" and a zipped archive file will be generated.

Well done! - you've created a database, a table and fields, entered in a few records, viewed the records, edited and perhaps deleted some of them and practised backing up.

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PhpMyAdmin Tutorial 2

2012-05-03T05:58:00.000-07:00

We will create a table in the database, called "people". Use the Create new table feature. Type in the name of the new table into the Name: people, and the number of columns in the table (4) into Fields:. This tutorial is only designed to show you the basic php/MySQL/phpMyAdmin functions. You can delete it using the Drop function. You will want to allow for growth in your table.

Click Go and you should see something like this. The table title now appears with under the database name.

Now enter the names and attributes of our table fields. Enter the following information as above:

Field	Type	Length	Default	Extra
id	int	6	0	auto_increment
name	char	100
telephone	char	50
birthday	char	50

The Length value indicates the maximum allowable length of characters for input. There are many different values that can be set for Type; see further documentation here. The Types specified in this example aren't the most efficient, but just used for the purposes of this exercise. The "id" field, which will be used as a Primary key for this table, has been set to auto_increment, saving you from having to having to type in the next number in sequence when you input records. Set the Default to 0

Once you've entered all the values, click Save. A screen like this will appear.

Congratulations!-You have created your table! The corresponding SQL command for creating these fields is also displayed. This isn't needed but in time you will start to recognise MySql commands
Note that you can use Drop to delete a table or fields.

When you are ready we suggest you check out all of the options on this page.

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PhpMyAdmin Tutorial 1

2012-05-03T05:55:00.003-07:00

PhpMyAdmin is web base software used for creating and maintaining MySQL databases.

This tutorial is designed to get you starting with the basics of phpMyAdmin.

You can access your MySQL account using phpMyAdmin using the link provided to you --something like below where my-domain.ca is your domain name

http://www.my-domain.ca/phpmyadmin/

When you click on the link above, a dialog box will prompt you for a username and password. This will be the username and password given you when we set it up for you.

Once you log in, a phpMyAdmin screen appears as shown below.

Creating a table in your database

The left-hand frame in phpMyAdmin is used for navigation.You will see your database displayed here (in this case called mydomain). As you create tables, they will show below this.

Click on your database the navigation frame and a new window will appear on the right hand side.

NEXT >>>

Get original URL referer with PHP

2012-05-02T06:24:00.000-07:00

Store it either in a cookie (if it's acceptable for your situation), or in a session variable.

<?php

  session_start();

  if (!isset($_SESSION["origURL"]))
    $_SESSION["origURL"] = $_SERVER["HTTP_REFERER"];
?>

$_SERVER['HTTP_REFERER']; to get the referer Url. It works as expected until the user clicks another page and the referer changes to the last page.

if more ways is there Please share here..................

PHP Interview questions 23

2012-05-02T06:14:00.000-07:00

96) what is MVC? why its been used?

Ans : Model-view-controller (MVC) is an architectural pattern used in software engineering. Successful use of the pattern isolates business logic from user interface considerations, resulting in an application where it is easier to modify either the visual appearance of the application or the underlying business rules without affecting the other. In MVC, the model represents the information (the data) of the application; the view corresponds to elements of the user interface such as text, checkbox items, and so forth; and the controller manages the communication of data and the business rules used to manipulate the data to and from the model. WHY ITS NEEDED IS 1 Modular separation of function 2 Easier to maintain 3 View-Controller separation means:

A Tweaking design (HTML) without altering code B â€” Web design staff can modify UI without understanding code

97) what is framework? how it works? what is advantage?

Ans : In general, a framework is a real or conceptual structure intended to serve as a support or guide for the building of something that expands the structure into something useful. Advantages : Consistent Programming Model Direct Support for Security Simplified Development Efforts Easy Application Deployment and Maintenance

98) what is CURL?

Ans : CURL means Client URL Library

curl is a command line tool for transferring files with URL syntax, supporting FTP, FTPS, HTTP, HTTPS, SCP, SFTP, TFTP, TELNET, DICT, LDAP, LDAPS and FILE. curl supports SSL certificates, HTTP POST, HTTP PUT, FTP uploading, HTTP form based upload, proxies, cookies, user+password authentication (Basic, Digest, NTLM, Negotiate, kerberos), file transfer resume, proxy tunneling and a busload of other useful tricks.

CURL allows you to connect and communicate to many different types of servers with many different types of protocols. libcurl currently supports the http, https, ftp, gopher, telnet, dict, file, and ldap protocols. libcurl also supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading (this can also be done with PHP’s ftp extension), HTTP form based upload, proxies, cookies, and user+password authentication.

99) what is PDO ?

Ans : The PDO ( PHP Data Objects ) extension defines a lightweight, consistent interface for accessing databases in PHP. if you are using the PDO API, you could switch the database server you used, from say PgSQL to MySQL, and only need to make minor changes to your PHP code.

While PDO has its advantages, such as a clean, simple, portable API but its main disadvantage is that it doesn't allow you to use all of the advanced features that are available in the latest versions of MySQL server. For example, PDO does not allow you to use MySQL's support for Multiple Statements.

Just need to use below code for connect mysql using PDO

try {

$dbh = new PDO("mysql:host=$hostname;dbname=databasename", $username, $password);

$sql = "SELECT * FROM employee";

foreach ($dbh->query($sql) as $row)

{

print $row['employee_name'] .' - '. $row['employee_age'] ;

}

catch(PDOException $e)

{

echo $e->getMessage();

}

100) What is PHP's mysqli Extension?

Ans : The mysqli extension, or as it is sometimes known, the MySQL improved extension, was developed to take advantage of new features found in MySQL systems versions 4.1.3 and newer. The mysqli extension is included with PHP versions 5 and later.

The mysqli extension has a number of benefits, the key enhancements over the mysql extension being:

=>Object-oriented interface

=>Support for Prepared Statements

=>Support for Multiple Statements

=>Support for Transactions

=>Enhanced debugging capabilities

=>Embedded server support

PHP Interview questions 22

2012-05-02T06:11:00.000-07:00

91) what is magic quotes?

Ans : Magic Quotes is a process that automagically escapes ncoming data to the PHP script. It’s preferred to code with magic quotes off and to instead escape the data at runtime, as needed. This feature has been DEPRECATED as of PHP 5.3.0 and REMOVED as of PHP 6.0.0. Relying on this feature is highly discouraged.

92) what is cross site scripting? SQL injection?

Ans : Cross-site scripting (XSS) is a type of computer security vulnerability typically found in web applications which allow code injection by malicious web users into the web pages viewed by other users. Examples of such code include HTML code and client-side scripts. SQL injection is a code injection technique that exploits a security vulnerability occurring in the database layer of an application. The vulnerability is present when user input is either incorrectly filtered for string literal escape characters embedded in SQL statements or user input is not strongly typed and thereby unexpectedly executed

93) what is URL rewriting?

Ans : Using URL rewriting we can convert dynamic URl to static URL Static URLs are known to be better than Dynamic URLs because of a number of reasons 1. Static URLs typically Rank better in Search Engines. 2. Search Engines are known to index the content of dynamic pages a lot slower compared to static pages. 3. Static URLs are always more friendlier looking to the End Users. along with this we can use URL rewriting in adding variables [cookies] to the URL to handle the sessions.

94) what is the major php security hole? how to avoid?

Ans : 1. Never include, require, or otherwise open a file with a filename based on user input, without thoroughly checking it first.

2. Be careful with eval() Placing user-inputted values into the eval() function can be extremely dangerous. You essentially give the malicious user the ability to execute any command he or she wishes!

3. Be careful when using register_globals = ON It was originally designed to make programming in PHP easier (and that it did), but misuse of it often led to security holes

4. Never run unescaped queries

5. For protected areas, use sessions or validate the login every time.

6. If you don’t want the file contents to be seen, give the file a .php extension.

95) whether PHP supports Microsoft SQL server ?

Ans : The SQL Server Driver for PHP v1.0 is designed to enable reliable, scalable integration with SQL Server for PHP applications deployed on the Windows platform. The Driver for PHP is a PHP 5 extension that allows the reading and writing of SQL Server data from within PHP scripts. using MSSQL or ODBC modules we can access Microsoft SQL server.

PHP Interview questions 21

2012-05-02T06:09:00.000-07:00

86) how to track no of user logged in ?

Ans : whenever a user logs in track the IP, userID etc..and store it in a DB with a active flag while log out or sesion expire make it inactive. At any time by counting the no: of active records we can get the no: of visitors.

87) in PHP for pdf which library used?

Ans : The PDF functions in PHP can create PDF files using the PDFlib library With version 6, PDFlib offers an object-oriented API for PHP 5 in addition to the function-oriented API for PHP 4. There is also the Â» Panda module. FPDF is a PHP class which allows to generate PDF files with pure PHP, that is to say without using the PDFlib library. F from FPDF stands for Free: you may use it for any kind of usage and modify it to suit your needs. FPDF requires no extension (except zlib to activate compression and GD for GIF support) and works with PHP4 and PHP5.

88) for image work which library?

Ans : we will need to compile PHP with the GD library of image functions for this to work. GD and PHP may also require other libraries, depending on which image formats you want to work with.

89) what is design pattern? singleton pattern?

Ans : A design pattern is a general reusable solution to a commonly occurring problem in software design.

The Singleton design pattern allows many parts of a program to share a single resource without having to work out the details of the sharing themselves.

90) what are magic methods?

Ans : Magic methods are the members functions that is available to all the instance of class Magic methods always starts with "__". Eg. __construct All magic methods needs to be declared as public To use magic method they should be defined within the class or program scope Various Magic Methods used in PHP 5 are: __construct() __destruct() __set() __get() __call() __toString() __sleep() __wakeup() __isset() __unset() __autoload() __clone()

PHP Interview questions 20

2012-04-30T08:11:00.000-07:00

81) How we load all classes that placed in different directory in one PHP File , means how to do auto load classes

Ans : by using spl_autoload_register('autoloader::funtion');

Like below

class autoloader

{

public static function moduleautoloader($class)

{

$path = $_SERVER['DOCUMENT_ROOT'] . "/modules/{$class}.php";

if (is_readable($path)) require $path;

}

public static function daoautoloader($class)

{

$path = $_SERVER['DOCUMENT_ROOT'] . "/dataobjects/{$class}.php";

if (is_readable($path)) require $path;

}

public static function includesautoloader($class)

{

$path = $_SERVER['DOCUMENT_ROOT'] . "/includes/{$class}.php";

if (is_readable($path)) require $path;

}

spl_autoload_register('autoloader::includesautoloader');

spl_autoload_register('autoloader::daoautoloader');

spl_autoload_register('autoloader::moduleautoloader');

82) How many types of Inheritances used in PHP and how we achieve it

Ans : As far PHP concern it only support single Inheritance in scripting.

we can also use interface to achieve multiple inheritance.

83) PHP how to know user has read the email?

Ans : Using Disposition-Notification-To: in mailheader we can get read receipt.

Add the possibility to define a read receipt when sending an email.

It’s quite straightforward, just edit email.php, and add this at vars definitions:

var $readReceipt = null;

And then, at â€˜createHeaderâ€™ function add:

if (!empty($this->readReceipt)) {

$this->__header .= â€˜Disposition-Notification-To: â€˜ . $this->__formatAddress($this->readReceipt) . $this->_newLine;

}

84) What are default session time and path?

Ans : default session time in PHP is 1440 seconds or 24 minutes

Default session save path id temporary folder /tmp

85) how to track user logged out or not? when user is idle ?

Ans : 85 By checking the session variable exist or not while loading th page. As the session will exist longer as till browser closes. The default behaviour for sessions is to keep a session open indefinitely and only to expire a session when the browser is closed. This behaviour can be changed in the php.ini file by altering the line session.cookie_lifetime = 0 to a value in seconds. If you wanted the session to finish in 5 minutes you would set this to session.cookie_lifetime = 300 and restart your httpd server.

PHP Interview questions 19

2012-04-30T08:09:00.000-07:00

76) What is the difference between char and varchar data types?

Ans : Set char to occupy n bytes and it will take n bytes even if u r storing a value of n-m bytes

Set varchar to occupy n bytes and it will take only the required space and will not use the n bytes

eg. name char(15) will waste 10 bytes if we store 'romharshan', if each char takes a byte eg. name varchar(15) will just use 5 bytes if we store 'romharshan', if each char takes a byte. rest 10 bytes will be free.

77) What is the functionality of md5 function in PHP?

Ans : Calculate the md5 hash of a string. The hash is a 32-character hexadecimal number. I use it to generate keys which I use to identify users etc. If I add random no techniques to it the md5 generated now will be totally different for the same string I am using.

78) How can I load data from a text file into a table?

Ans : you can use LOAD DATA INFILE file_name; syntax to load data from a text file. but you have to make sure thata) data is delimited

b) columns and data matched correctly

79) How can we know the number of days between two given dates using MySQL?

Ans : SELECT DATEDIFF("2007-03-07","2005-01-01");

80) How can we know the number of days between two given dates using PHP?

Ans : $date1 = date("Y-m-d");

$date2 = "2006-08-15";

$days = (strtotime($date1) - strtotime($date2)) / (60 * 60 * 24);

PHP Interview questions 18

2012-04-30T08:07:00.001-07:00

71) What type of inheritance that PHP supports?

Ans : In PHP an extended class is always dependent on a single base class, that is, multiple inheritance is not supported. Classes are extended using the keyword 'extends'.

72) What is the difference between Primary Key and Unique key?

Ans : Primary Key: A column in a table whose values uniquely identify the rows in the table. A primary key value cannot be NULL.

Unique Key: Unique Keys are used to uniquely identify each row in the table. There can be one and only one row for each unique key value. So NULL can be a unique key.There can be only one primary key for a table but there can be more than one unique for a table.

73) what is garbage collection? default time ? refresh time?

Ans : Garbage Collection is an automated part of PHP , If the Garbage Collection process runs, it then analyzes any files in the /tmp for any session files that have not been accessed in a certain amount of time and physically deletes them. Garbage Collection process only runs in the default session save directory, which is /tmp. If you opt to save your sessions in a different directory, the Garbage Collection process will ignore it. the Garbage Collection process does not differentiate between which sessions belong to whom when run. This is especially important note on shared web servers. If the process is run, it deletes ALL files that have not been accessed in the directory. There are 3 PHP.ini variables, which deal with the garbage collector: PHP ini value name default session.gc_maxlifetime 1440 seconds or 24 minutes session.gc_probability 1 session.gc_divisor 100

74) What are the advantages/disadvantages of MySQL and PHP?

Ans : Both of them are open source software (so free of cost), support cross platform. php is faster then ASP and JSP.

75) What is the difference between GROUP BY and ORDER BY in Sql?

Ans : ORDER BY [col1],[col2],â€¦,[coln]; Tels DBMS according to what columns it should sort the result. If two rows will hawe the same value in col1 it will try to sort them according to col2 and so on.GROUP BY [col1],[col2],â€¦,[coln]; Tels DBMS to group results with same value of column col1. You can use COUNT(col1), SUM(col1), AVG(col1) with it, if you want to count all items in group, sum all values or view average

PHP Interview questions 17

2012-04-30T08:06:00.000-07:00

66) Explain Normalization concept?

Ans : The normalization process involves getting our data to conform to three progressive normal forms, and a higher level of normalization cannot be achieved until the previous levels have been achieved (there are actually five normal forms, but the last two are mainly academic and will not be discussed).First Normal FormThe First Normal Form (or 1NF) involves removal of redundant data

from horizontal rows. We want to ensure that there is no duplication of data in a given row, and that every column stores the least amount of information possible (making the field atomic).Second Normal FormWhere the First Normal Form deals with redundancy of data across a horizontal row, Second Normal Form (or 2NF) deals with redundancy of data in vertical columns. As stated earlier, the normal forms are progressive, so to achieve Second Normal Form, your tables must already be in First Normal Form.Third Normal Form I have a confession to make; I do not often use Third Normal Form. In Third Normal Form we are looking for data in our tables that is not fully dependant on the primary key, but dependant on another value in the table

67) How can we find the number of rows in a table using MySQL?

Ans : Use this for mysql

>SELECT COUNT(*) FROM table_name;

68) How can we find the number of rows in a result set using PHP?

Ans : $result = mysql_query($sql, $db_link);

$num_rows = mysql_num_rows($result);

echo "$num_rows rows found";

69) How many ways we can we find the current date using MySQL?

Ans : 69 SELECT CURDATE();

CURRENT_DATE() = CURDATE()

for time use

SELECT CURTIME();

CURRENT_TIME() = CURTIME()

70) What are the advantages and disadvantages of Cascading Style Sheets?

Ans : External Style SheetsAdvantagesCan control styles for multiple documents at once. Classes can be

created for use on multiple HTML element types in many documents. Selector and grouping methods can be used to apply styles under complex contextsDisadvantagesAn extra download is required to import style information for each document The rendering of the document may be delayed until the external style sheet is loaded Becomes slightly unwieldy for small quantities of style definitionsEmbedded Style Sheets Advantages Classes can be created for use on multiple tag types in the document.

Selector and grouping methods can be used to apply styles under complex contexts. No additional downloads necessary to receive style information

Disadvantages

This method can not control styles for multiple documents at once Inline Styles

Advantages

Useful for small quantities of style definitions. Can override other style specification methods at the local level so only exceptions need to be listed in conjunction with other style methods

Disadvantages

Does not distance style information from content (a main goal of SGML/HTML). Can not control styles for multiple documents at once.

Author can not create or control classes of elements to control multiple element types within the document. Selector grouping methods can not be used to create complex element addressing scenarios

PHP Interview questions 16

2012-04-30T08:03:00.001-07:00

61) What are the other commands to know the structure of table using MySQL commands except explain command?

Ans : describe Table-Name;

62) How many tables will create when we create table, what are they?

Ans : The '.frm' file stores the table definition.

The data file has a '.MYD' (MYData) extension.

The index file has a '.MYI' (MYIndex) extension,

63) What is the purpose of the following files having extensions 1) .frm 2) .myd 3) .myi? What do these files contain?

Ans : In MySql, the default table type is MyISAM.

Each MyISAM table is stored on disk in three files. The files have names that begin with the table name and have an extension to indicate the file type.

The '.frm' file stores the table definition.

The data file has a '.MYD' (MYData) extension.

The index file has a '.MYI' (MYIndex) extension,

64) What is maximum size of a database in MySQL?

Ans : If the operating system or filesystem places a limit on the number of files in a directory, MySQL is bound by that constraint.The efficiency of the operating system in handling large numbers of files in a directory can place a practical limit on the number of tables in a database. If the time required to open a file in the directory increases significantly as the number of files increases, database performance can be adversely affected.

The amount of available disk space limits the number of tables.

MySQL 3.22 had a 4GB (4 gigabyte) limit on table size. With the MyISAM storage engine in MySQL 3.23, the maximum table size was increased to 65536 terabytes (2567 â€“ 1 bytes). With this larger allowed table size, the maximum effective table size for MySQL databases is usually determined by operating system constraints on file sizes, not by MySQL internal limits.The InnoDB storage engine maintains InnoDB tables within a tablespace that can be created from several files. This allows a table to exceed

the maximum individual file size. The tablespace can include raw disk partitions, which allows extremely large tables. The maximum tablespace size is 64TB.

The following table lists some examples of operating system file-size limits. This is only a rough guide and is not intended to be definitive. For the most up-to-date information, be sure to check the documentation specific to your operating system.

Operating System File-size LimitLinux 2.2-Intel 32-bit 2GB (LFS: 4GB)

Linux 2.4+ (using ext3 filesystem) 4TB

Solaris 9/10 16TB

NetWare w/NSS filesystem 8TB

Win32 w/ FAT/FAT32 2GB/4GB

Win32 w/ NTFS 2TB (possibly larger)

MacOS X w/ HFS+ 2TB

65) Give the syntax of Grant and Revoke commands?

Ans : The generic syntax for grant is as following

> GRANT [rights] on [database/s] TO [username@hostname] IDENTIFIED BY [password] now rights can be

a) All privileges

b) combination of create, drop, select, insert, update and delete etc.We can grant rights on all databse by using *.* or some specific database by database.* or a specific table by database.table_name

username@hotsname can be either username@localhost, username@hostname and username@%

where hostname is any valid hostname and % represents any name, the *.* any condition password is simply the password of userThe generic syntax for revoke is as following > REVOKE [rights] on [database/s] FROM [username@hostname] now rights can be as explained above

a) All privileges

b) combination of create, drop, select, insert, update and delete etc.

username@hotsname can be either username@localhost, username@hostname and username@%

where hostname is any valid hostname and % represents any name, the *.*

any condition