SELECT * FROM MYTAB A WHERE A.COL1 = :COL1 AND A.COL2 = :COL2
SELECT * FROM MYTAB A WHERE (A.COL1 = :COL1 OR (A.COL1 IS NULL AND :COL1 IS NULL)) AND (A.COL2 = :COL2 OR (A.COL2 IS NULL AND :COL2 IS NULL))