The IS [NOT] NULL operator can be used in WHERE clause predicates to match or exclude null values occurring in a specified data column. Its syntax is as follows (where x is typically a column name):
The query below retrieves all Part table records that do not have a null value in their color data column:
WHERE color IS NOT NULL;
When used in a predicate, the NULL operator keyword must be preceded with either the IS or IS NOT keywords. Operators such as = or != cannot be used with the NULL keyword.