Returns true (.T.) if an expression evaluates to a null value; otherwise, ISNULL( ) returns false (.F.).
Syntax
ISNULL(eExpression)
Returns
Logical
Arguments
eExpression
Specifies the expression to evaluate.
Remarks
Use ISNULL( ) to determine if the contents of a field, memory variable, or array element contains a null value, or if an expression evaluates to a null value.