Operator to check if value is NULL

IS NULL operator allows you to check if the left-side expression value is NULL. If the value is NULL, the operator returns TRUE; else — FALSE. You can inverse operator action by using NOT.

See also: Logical Expressions

Example:

SELECT
Catalog.Nomenclature.Description,
   Catalog.Nomenclature.ProcurementPrice
WHERE
   Catalog.Nomenclature.ProcurementPrice IS NULL