資料表：
dept:deptno(primary key), dname, loc
emp:empno(primary key), ename, job, mgr(references emp(empno)), sal,deptno(references dept(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、對於emp中最低工資小於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，工資由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、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')

6、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

7、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'
 

8、對於emp中有管理者的員工，列出姓名，管理者姓名（管理者外來鍵為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

9、對於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'

10、對於工資高於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

11、對於emp，列出各個部門中平均工資高於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

12、對於emp中工資高於本部門平均水平，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

13、對於emp中低於自己工資至少5人的員工，列出其部門號，姓名，工資，以及工資少於自己的人數

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