Oracle UNION和INTERSECT以及MINUS

1、UNION取得两个结果集的并集并去掉重复行 AUB

SELECT ename,job,sal FROM emp WHERE sal>2500 UNION
SELECT ename,job,sal FROM emp WHERE job='MANAGER' ORDER BY 1;

等同于
SELECT ename,job,sal FROM emp WHERE sal>2500 OR job='MANAGER' ORDER BY 1;

UNION ALL取得两个结果集的并集并不去掉重复行
SELECT ename,job,sal FROM emp WHERE sal>2500 UNION ALL
SELECT ename,job,sal FROM emp WHERE job='MANAGER' ORDER BY 1;

2、INTERSECT取得两个结果集的交集 A交B

SELECT ename,job,sal FROM emp WHERE sal>2500 INTERSECT
SELECT ename,job,sal FROM emp WHERE job='MANAGER' ORDER BY 1;

等同于
SELECT ename,job,sal FROM emp WHERE sal>2500 AND job='MANAGER' ORDER BY 1;

3、MINUS取得两个集合的差集，只显示在集合A中的数据，并且不属于集合B的数据
SELECT ename,job,sal FROM emp WHERE sal>2500 MINUS
SELECT ename,job,sal FROM emp WHERE job='MANAGER' ORDER BY 1;

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