Poti face diferenta cu un simplu LEFT | RIGHT OUTER JOIN.

Exemplu:

CREATE TABLE T1 (C1 CHAR(1), C2 INT)
CREATE TABLE T2 (C1 CHAR(1), C2 INT)

INSERT INTO T1 (C1, C2)
SELECT Q.C1, Q.C2
FROM
(
SELECT 'A' AS C1, 101 AS C2
UNION
SELECT 'B', 102
UNION
SELECT 'C', 103
UNION
SELECT 'D', 104
UNION
SELECT 'E', 105
) AS Q

INSERT INTO T2 (C1, C2)
SELECT Q.C1, Q.C2
FROM
(
SELECT 'A' AS C1, 101 AS C2
UNION
SELECT 'B', 102
UNION
SELECT 'X', 106
) AS Q

--DIFERENTA PROPRIU-ZISA; T1-T2 = INREGISTRARILE DIN T1 CARE NU SUNT IN T2
SELECT T1.C1, T1.C2
FROM T1 LEFT OUTER JOIN T2 ON T1.C1 = T2.C1 AND T1.C2 = T2.C2
WHERE T2.C1 IS NULL