Someone

CREATE TABLE t1 (id int);CREATE TABLE t2 (id int);INSERT INTO t1 VALUES (1), (2), (2);INSERT INTO t2 VALUES (2), (3);SELECT t1.id, t2.id FROM t1 LEFT JOIN t2 USING (id)UNION ALLSELECT t1.id, t2.id FROM t1 RIGHT JOIN t2 USING (id);/*+------+------+| id   | id   |+------+------+|    1 | NULL ||    2 |    2 ||    2 |    2 ||    2 |    2 ||    2 |    2 || NULL |    3 |+------+------+6 rows in set (0.00 sec)Too many.*/SELECT t1.id, t2.id FROM t1 LEFT JOIN t2 USING (id)UNIONSELECT t1.id, t2.id FROM t1 RIGHT JOIN t2 USING (id);/*+------+------+| id   | id   |+------+------+|    1 | NULL ||    2 |    2 || NULL |    3 |+------+------+3 rows in set (0.00 sec)Too few.*/select * from t1 left outer join t2 on (t1.id=t2.id)  union all select * from t1 right outer join t2 on (t1.id=t2.id) where t1.id is null;/*+------+------+| id   | id   |+------+------+|    1 | NULL ||    2 |    2 ||    2 |    2 || NULL |    3 |+------+------+4 rows in set (0.00 sec)*/