Logical functions SQL Function Description boolean1 or boolean2 Returns TRUE if boolean1 is TRUE or boolean2 is TRUE. Supports three-valued logic. For example: SELECT c1, c2, c1 OR c2 AS or_result FROM (VALUES (TRUE, CAST(UNKNOWN AS BOOLEAN))) AS t(c1,c2); c1 c2 or_result TRUE <NULL> TRUE boolean1 and boolean2 Returns TRUE if boolean1 and boolean2 are both TRUE. Supports three-valued logic. For example: SELECT c1, c2, c1 AND c2 AS and_result FROM (VALUES (TRUE, CAST(UNKNOWN AS BOOLEAN))) AS t(c1,c2); c1 c2 and_result TRUE <NULL> <NULL> NOT boolean Returns TRUE if boolean is FALSE; returns FALSE if boolean is TRUE; returns UNKNOWN if boolean is UNKNOWN. boolean IS FALSE Returns TRUE if boolean is FALSE; returns FALSE if boolean is TRUE or UNKNOWN. boolean IS NOT FALSE Returns TRUE if boolean is TRUE or UNKNOWN; returns FALSE if boolean is FALSE. boolean IS TRUE Returns TRUE if boolean is TRUE; returns FALSE if boolean is FALSE or UNKNOWN. boolean IS NOT TRUE Returns TRUE if boolean is FALSE or UNKNOWN; returns FALSE if boolean is TRUE. boolean IS UNKNOWN Returns TRUE if boolean is UNKNOWN; returns FALSE if boolean is TRUE or FALSE. boolean IS NOT UNKNOWN Returns TRUE if boolean is TRUE or FALSE; returns FALSE if boolean is UNKNOWN.