You would use Is Null and Is Not Null in query expressions and SQL WHERE clauses. IsNull(), on the other hand, is a Visual Basic for Applications (VBA) function and would be used only in VBA modules.

IS NULL and IS MISSING are used in the WHERE, ON, and HAVING expressions. Each predicate resolves to true if the sql-expression's result is missing and false if it is not missing. SAS stores a numeric ...