To find nth highest salary use below code.

SELECT * FROM emp employee1 WHERE n = (SELECT COUNT(DISTINCT (employee2.salary) FROM emp employee2 WHERE employee2.salary >= employee1.salary))

use find 2th highest salary put only 2 on the place of n on the above query.
the query will become

SELECT  * FROM emp employee1 WHERE 2 = (SELECT COUNT(DISTINCT (employee2.salary) FROM emp employee2 WHERE employee2.salary >= employee1.salary))

for 3,4,5 ……, put exact number on the place of n on the above query.

ID attribute play very important rule in web page.
In a web page every web element must have unique id.

Ex-<input type=”text” name=”text1” id=”text1”/>
<input type=”text” name=”text2” id=”text2”/>

To  get value of above  textbox from #id selector using jquery need to write below code.

var value=$(“# text1”).val();

another example, To apply css on #myDivId element use below code.

$(“#myDivId”).css(“border”,”3px solid red”);

There are number of ways to use Ajax in JQuery library

GET Oriented Method:
If you want Ajax activity either on load page, submit form, paging what ever. It depend on you
Use below code

$. get (“back.php”, {name1: “php”, name2: “interview”},
function(data){
alert(“Data Loaded: ” + data);
});

Where
back.php = back file need to call.
name1: “php”, name1: “interview” = values to send on back.php.
data = value which back.php will return.

Please see look on back.php

POST Oriented Method:

Please changes $.get to $.post in above code.

Third method:

This is third method to use Ajax using JQuery library.

$.ajax({
type: “POST”,
Url: “back.php”,
data: “name=php&location=India”,
success:function (msg){
alert( “Data Saved: ” + msg);
}
});

This is the example, how to download pdf file using php. you can also use this code for zip file,word file,image file, any type of media file.

$filename=”directory/filename”;//In $filename will have to  provide full path of file.

header(“Pragma: public”);

header(“Expires: 0″);

header(“Cache-Control: must-revalidate, post-check=0, pre-check=0″);

header(“Content-Type: application/force-download”);

header(“Content-Type: application/octet-stream”);

header(“Content-Type: application/download”);

header(“Content-Disposition: attachment; filename=”.basename($filename).”;”);

header(“Content-Transfer-Encoding: binary”);

header(“Content-type: application/pdf”);

header(“Content-Length: “.filesize($filename));

readfile(“$filename”);

exit();

If your file is pdf then use header(“Content-type: application/pdf”);

If zip file then use  header(“Content-type: application/zip”);

In $filename provide full path of file.

Ex. If your file is in  pdf folder and your php file is in  outside of pdf folder.

Then $filename=”pdf/filename.pdf”;//  will be.

If you want to display file not download, You have to remove below header  from above code.

header(“Content-Disposition: attachment; filename=”.basename($filename).”;”);

Both are  used to includes files once. Means PHP will check if the file has already been included, and if so, not include (include) it again.

include _once() create  warning  if file not found and  execute   script.

require_once() create fatal  error  if file not found and  terminate  script.

Require()

The  Require() is  used to include a file, It create fatal  error if file not found and  terminate  script.

require_once()

The require_once() to require() except PHP will check if the file has already been included, and  if so, tricor online not include (require) it again.

include ()

The include ()  is  used to include a file, It create warning  if file not found and  execute   script.

include_once()

The include _once() statement include () except PHP will check if the file has already been included, and if so, not include (include) it again.

There are  4 methods to includes  files

require()

require_once()

include()

include_once()

There are  number of superglobal variables in php

• $GLOBALS
• $_SERVER
• $_GET
• $_POST
• $_FILES
• $_COOKIE
• $_SESSION
• $_REQUEST
• $_ENV

Juggling means

throwing and catching several objects simultaneously.

Type Juggling in php  means automatically type conversion.

That is to say, if a string value is assigned to variable $var,  $var becomes a string. If an integer  value is assigned to $var, it becomes an integer.

Please see Example.

<?php
$var = "0";// $var is string (ASCII 48)
$var += 10; // $var is now an integer (10)
$var = $foo+ 1.5; // $var is now a float (11.5)
$var = 5 + "10 Little hots"; // $var  is integer (15)
$ var = 5 + "10 Small hots"; // $var  is integer (15)
?>

$var variable comes many times in different data type.

Often it became interger, float.

This is Type Juggling in php.

Thank you

PHP supports 8  data  types.

• boolean
• integer
• float (floating-point number, aka double)
• string
• array
• object
• resource
• NULL

Explaination:

4 scalar types:

boolean

<?php

$var = True; // assign the value TRUE to $foo
?>

integer

<?php
$var = 123; // decimal number
$var = -122; // a negative number
$var = 0111; // octal number
$var = 0x1B; // hexadecimal number

?>

float (floating-point number, aka double)

<?php
$var = 1.234;
$var= 1.2e3;
$var = 7E-10;
?>

string

<?php
$string =”Hello World”;  // Assign Hello World into $string

?>

2 compound types:

array

<?php
$array = array(“first”=>”Hello”,”second”=>”World”);

echo $array[‘first’];

echo $array[‘second];

?>

object

<?php

Class Interview

{

Function php()

{

Echo “What  is php”;

}

}

$obj = new Interview(); // $obj is object , you can also take different name   like  $object,$interview

Echo $obj-> php();

?>

3 compound types:

resource

NULL

<?php
$variable = NULL;
?>

Note:  PHP does not require to define variable in in any specific data type. Like  integer,float,string etc, like C,C++.

PHP  support   automatic type conversion .
For More Detail see Type Juggling articles.

Thank you