NULL predicate 

By specifying a NULL predicate, you can test whether the value is a NULL value.

Syntax

<null_predicate> ::= <expression> IS [NOT] NULL

Examples

SQL Tutorial, Negative Conditions: NOT

Explanation

The truth content of a NULL predicate is either true or false.

	Result of the function x IS NULL
x is NULL value	true
x is a special NULL value	false

 

x IS NOT NULL has the same result as NOT(x IS NULL).