oracle集合运算详解

一、union求并集，公共部分只有包含一次

例：求emp表ename中含’A‘或含有‘M’

SQL> select * from emp where ename like '%A%'

2 union

3 select * from emp where ename like '%M%';

二、union all求集并，公共部分只有包含二次

例：求emp表ename中含’A‘或含有‘M’

SQL> select * from emp where ename like '%A%'

2 union all

3 select * from emp where ename like '%M%';

三、intersect求交集，只有包含公共部分

例：求emp表ename中即含’A‘又含有‘M’

SQL> select * from emp where ename like '%A%'

intersect

select * from emp where ename like '%M%';

四、minus求差集，求集合A去除集合A和集合B的交集

例：求emp表sal从700到1200

SQL>select * from emp where sal between 700 and 1300

minus

select * from emp where sal between 1200 and 1400;