Checks whether the specified expression has a null value. This function takes an expression argument of any type and returns a Boolean value. If the expression is null, the function returns the Boolean value TRUE. If the expression has a value, it returns the Boolean value FALSE.

Syntax

IsNull(<expression>)

Input

expression

expression

The expression to check.

Output

Boolean

Examples

Assume that you have a form in which there is a number question with the reference name number_of_cars.

• If this question is not answered, the expression IsNull($number_of_cars) returns TRUE because the answer is null, meaning that it does not contain a value of any type.
• If the question is instead answered 2, the expression IsNull($number_of_cars) returns FALSE because the answer contains a value.