Example (Microsoft SQL Server):
CREATE TABLE foo ( id int );
SELECT * FROM foo WHERE NULL = NULL;
SELECT * FROM foo WHERE NULL != NULL;
The NULL = NULL can be replaced with IS NULL, the NULL != NULL comparison
with IS NOT NULL. To do this replacement, you can use Use IS NULL operator or Use IS NOT NULL operator
quick-fixes.
SELECT * FROM foo WHERE NULL IS NULL;
SELECT * FROM foo WHERE NULL IS NOT NULL;