ifnull

Retrieve an expression if another expression is null

Syntax

IFNULL(value_expr1, value_expr2)

Arguments

value_expr1	The expression to be evaluated and, if not null, returned.
value_expr2	The expression to be evaluated and returned if value_expr1 is null.

Description

This system function retrieves the value of the first specified expression (value_expr1) if it is not null. If value_expr1 is null, the IFNULL function returns the value of second expression (value_expr2). The two expressions must be of compatible data types.