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).