/*
建表：
dept:
?deptno(primary key),dname,loc
emp:
?empno(primary key),ename,job,mgr,sal,deptno
*/
1 列出emp表中各部門的部門號，最高工資，最低工資
select max(sal) as 最高工資,min(sal) as 最低工資,deptno from emp group by deptno;
2 列出emp表中各部門job為'CLERK'的員工的最低工資，最高工資
select max(sal) as 最高工資,min(sal) as 最低工資,deptno as 部門號 from emp where job = 'CLERK' group by deptno;
3 對于emp中最低工資小于1000的部門，列出job為'CLERK'的員工的部門號，最低工資，最高工資
select max(sal) as 最高工資,min(sal) as 最低工資,deptno as 部門號 from emp as b
where job='CLERK' and 1000>(select min(sal) from emp as a where a.deptno=b.deptno) group by b.deptno
4 根據部門號由高而低，工資有低而高列出每個員工的姓名，部門號，工資
select deptno as 部門號,ename as 姓名,sal as 工資 from emp order by deptno desc,sal asc
5 寫出對上題的另一解決方法
（請補充）
6 列出'張三'所在部門中每個員工的姓名與部門號
select ename,deptno from emp where deptno = (select deptno from emp where ename = '張三')
7 列出每個員工的姓名，工作，部門號，部門名
select ename,job,emp.deptno,dept.dname from emp,dept where emp.deptno=dept.deptno
8 列出emp中工作為'CLERK'的員工的姓名，工作，部門號，部門名
select ename,job,dept.deptno,dname from emp,dept where dept.deptno=emp.deptno and job='CLERK'
9 對于emp中有管理者的員工，列出姓名，管理者姓名（管理者外鍵為mgr）
select a.ename as 姓名,b.ename as 管理者 from emp as a,emp as b where a.mgr is not null and a.mgr=b.empno
10 對于dept表中，列出所有部門名，部門號，同時列出各部門工作為'CLERK'的員工名與工作
select dname as 部門名,dept.deptno as 部門號,ename as 員工名,job as 工作 from dept,emp
where dept.deptno *= emp.deptno and job = 'CLERK'
11 對于工資高于本部門平均水平的員工，列出部門號，姓名，工資，按部門號排序
select a.deptno as 部門號,a.ename as 姓名,a.sal as 工資 from emp as a
where a.sal>(select avg(sal) from emp as b where a.deptno=b.deptno) order by a.deptno
12 對于emp，列出各個部門中平均工資高于本部門平均水平的員工數和部門號，按部門號排序
select count(a.sal) as 員工數,a.deptno as 部門號 from emp as a
where a.sal>(select avg(sal) from emp as b where a.deptno=b.deptno) group by a.deptno order by a.deptno
13 對于emp中工資高于本部門平均水平，人數多與1人的，列出部門號，人數，按部門號排序
select count(a.empno) as 員工數,a.deptno as 部門號,avg(sal) as 平均工資 from emp as a
where (select count(c.empno) from emp as c where c.deptno=a.deptno and c.sal>(select avg(sal) from emp as b where c.deptno=b.deptno))>1
group by a.deptno order by a.deptno
14 對于emp中低于自己工資至少5人的員工，列出其部門號，姓名，工資，以及工資少于自己的人數
select a.deptno,a.ename,a.sal,(select count(b.ename) from emp as b where b.sal<a.sal) as 人數 from emp as a
where (select count(b.ename) from emp as b where b.sal<a.sal)>5