-- today ------------------------------------------------------------------------
-- 多行子查询
-- in
-- 查询是经理的姓名，工资
select ename,sal
from emp
where empno in (select mgr from emp)
-- 查询不是经理的姓名，工资
-- 注意：not in（不能为空）
select ename,sal
from emp
where empno not in (select mgr from emp where mgr is not null)
-- ANY : =any(和in意思相同)
-- 查询工资高于10部门任意一名员工
select *
from emp
where sal >any(select sal from emp where deptno = 10)
-- all 了解
-- 查询工资高于20部门所有员工
select *
from emp
where sal >all(select sal from emp where deptno = 20)
-- 注意：当子查询返回一条以上的记录时不可以用<,>,=,>=,<=,!=
-- 多列子查询
-- 9.查询员工工资为其部门最低工资的员工的编号和姓名及工资。
select ename,sal
from emp
where (deptno,sal)
in (select deptno,min(sal) from emp GROUP BY deptno )
-- 16. 显示每个部门的最高工资的员工
select ename,sal
from emp
where (deptno,sal)
in (select deptno,max(sal) from emp GROUP BY deptno )
select ename,sal
from emp e
join (select deptno,max(sal) maxsal from emp GROUP BY deptno ) d
on e.deptno = d.deptno
where sal = maxsal
-- 查询可以当表使用，查询到的数据可以理解为表的数据
-- 查询比自己部门平均工资高的员工姓名，工资，部门平均工资
select e.deptno,ename,sal,avgsal
from emp e
join (select deptno,AVG(sal) avgsal from emp GROUP BY deptno) d
on e.deptno = d.deptno
where sal > avgsal
-- 相关子查询
-- 查询每个部门工资最高的姓名工资
select empno,ename,sal,deptno
from emp
where (deptno,sal) in (select deptno,max(sal) from emp GROUP BY deptno )
select ename,sal
from emp e
join (select deptno,max(sal) maxsal from emp GROUP BY deptno ) d
on e.deptno = d.deptno
where sal = maxsal
-- 相关
select empno,ename,sal,deptno
from emp e
where sal=(select max(sal) from emp where deptno= e.deptno)
-- 查询比自己部门平均工资高的员工姓名，工资，部门平均工资
select e.deptno,ename,sal,avgsal
from emp e
join (select deptno,AVG(sal) avgsal from emp GROUP BY deptno) d
on e.deptno = d.deptno
where sal > avgsal
-- 显示部门和人数
select dname,count(empno)
from emp
join dept
on dept.deptno = emp .deptno
GROUP BY dname
select dname, (select count(deptno) from emp where deptno = e.deptno ) renshu
from dept e
3.列出001号成绩比002号成绩分数高的所有学生学号
select s1.sno
from SC s1
group by s1.sno
having (select scgrade from sc c where cno = 001 and s1.sno= c.sno ) > (select scgrade from sc c where cno = 002 and s1.sno= c.sno)
-- 5.删除学生 表中同名的学员，只保留SNO最大的记录
delete from s
where sno not in (
select maxsno from ( select MAX(sno) maxsno from s group by sname ) s