Web developers notes,programming tutorials.

isNaN(testvalue)
 
The isNaN function is used to determine if the argument, testvalue, is a NaN.
 
A NaN, which means “Not-a-Number”, is classified as a primitive value by the ECMA-262 standard and indicates that the specified value is not a legal number. The function returns true if the argument is not a number and false if the argument is a number.
 
The classic example of a NaN is zero divided by zero, 0/0.
 
Code:
document.write(isNaN(”Ima String”))
document.write(isNaN(0/0))
document.write(isNaN(”348″))
document.write(isNaN(348))
 
Output:
true
true
false
false

Working with sessions in PHP is very basic. You can store values to session as key/value pairs.
To store and receive data from sessions are very easy to use.

Start Session
session_start();
$_SESSION['PHPSESSID'] = "123456";

Retrieve Value:
session_start();
echo $_SESSION['mySessionName'];

There are three types of subqueries, differentiated by how many rows and columns they return.

1. Scalar subqurey
2. Row subquery
3. Table subquery

Scalar subquery :
If a subquery returns exactly one column and one row, it is known as a scalar subquery.

Row subquery :
If a subquery returns multiple columns and exactly one row, it is known as a row subquery. A row subquery is a derivation of a scalar subquery and can thus be used anywhere that a scalar subquery can be used.

Table subquery :
if a subquery can return multiple columns and multiple rows, it is known as a table subquery. A table subquery is legal everywhere that a table reference is legal in an SQL statement, including the FROM clause of a SELECT. It, too, is usually found in a WHERE clause, immediately after an IN or EXISTS predicate or a quantified comparison operator.