Question

数据库中 查询结果的 并集,交集是怎么写的啊，用的什么关键字

最好拿一个举个例子就更好了

Answer 1

A 并 B 去掉重复记录----union
select empno, ename ,salary ,deptno from employee_ccy where deptno=10
union
select empno, ename ,salary ,deptno from employee_ccy where salary>100;

－－union all 不排序，不去重复

select empno, ename ,salary ,deptno from employee_ccy where deptno=10 union all
select empno, ename ,salary ,deptno from employee_ccy where salary>100;

－－－交集-----intersect
select empno, ename ,salary ,deptno from employee_ccy where deptno=10
intersect
select empno, ename ,salary ,deptno from employee_ccy where salary>100;

--差集--------minus
select empno, ename ,salary ,deptno from employee_ccy where deptno=10
minus
select empno, ename ,salary ,deptno from employee_ccy where salary>100;

-------------用两个结果集的差集 ，获得
select deptno,dname ,location from department_ccy where deptno in(select deptno from department_ccy
minus
select distinct deptno from employee_ccy );

希望对你有帮助

Answer 2

“与”、“或”、“非”，例如交集用‘与’

Answer 3

并集union 或 union all 前者去重后者不去重
交集intersect
差集minus
比如oracle的例子
http://wenku.baidu.com/view/0f2880bc960590c69ec37603.html