To test for NULL, use the IS NULL and IS NOT NULL operators
SELECT 1 IS NULL, 1 IS NOT NULL;
You cannot use arithmetic comparison operators such as =, <, or <> to test for NULL.
SELECT 1 = NULL, 1 <> NULL, 1 < NULL, 1 > NULL;
To test for NULL, use the IS NULL and IS NOT NULL operators
SELECT 1 IS NULL, 1 IS NOT NULL;
You cannot use arithmetic comparison operators such as =, <, or <> to test for NULL.
SELECT 1 = NULL, 1 <> NULL, 1 < NULL, 1 > NULL;