MySQL面试题(二)

--
-- 转存表中的数据 `dept`
--
INSERT INTO `dept` (`deptno`, `dname`) VALUES
('1', '事业部'),
('2', '销售部'),
('3', '技术部');

--
-- 转存表中的数据 `emp`
--

INSERT INTO `emp` (`empno`, `ename`, `job`, `mgr`, `sal`, `deptno`) VALUES
('01', 'jacky', 'clerk', 'tom', '1000', '1'),
('02', 'tom', 'clerk', 'tom', '2000', '1'),
('03', 'jenny', 'sales', 'pretty', '1000', '2'),
('04', 'pretty', 'sales', '', '800', '2'),
('05', 'buddy', 'jishu', 'canndy', '1000', '3'),
('06', 'canddy', 'jishu', '', '1000', '3'),
('07', 'biddy', 'clerk', 'tom', '2000', '1');

insert into emp values ('01','jacky','clerk','tom','1000','1');
+--------------+-----------+
| 员工名称     | 管理员    |
+--------------+-----------+
| tom          | jacky     |
| tom          | tom       |
| pretty       | jenny     |
|              | pretty    |
| canndy       | buddy     |
|              | canddy    |
| tom          | biddy     |
+--------------+-----------+
7 rows in set (0.00 sec)

select b.dname as '部门名称',b.deptno as '部门编号',a.ename as '员工名称',
a.job as '工作岗位' from emp a  inner join dept b  on a.deptno = b.deptno
and  a.job='clerk';
+--------------+--------------+--------------+--------------+
| 部门名称     | 部门编号     | 员工名称     | 工作岗位     |
+--------------+--------------+--------------+--------------+
| 事业部       | 1            | jacky        | clerk        |
| 事业部       | 1            | tom          | clerk        |
| 事业部       | 1            | biddy        | clerk        |
+--------------+--------------+--------------+--------------+
3 rows in set (0.00 sec)

select a.deptno as '部门编号',b.dname as '部门名称',a.ename as '员工姓名',
a.sal as '员工工资' from emp a inner join dept b on a.deptno = b.deptno 
where a.sal>(select avg(sal) as sal from emp)  order by a.deptno;
+--------------+--------------+--------------+--------------+
| 部门编号     | 部门名称     | 员工姓名     | 员工工资     |
+--------------+--------------+--------------+--------------+
| 1            | 事业部       | tom          | 2000         |
| 1            | 事业部       | biddy        | 2000         |
+--------------+--------------+--------------+--------------+
2 rows in set (0.01 sec)

select count(a.empno) as '员工数量',a.deptno as '部门编号',avg(sal) as '平均工资' 
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;  
+--------------+--------------+--------------------+
| 员工数量     | 部门编号     | 平均工资           |
+--------------+--------------+--------------------+
|            3 | 1            | 1666.6666666666667 |
+--------------+--------------+--------------------+
1 row in set (0.00 sec)

select b.deptno as '部门号',c.dname as '部门名称', b.ename as '姓名', 
b.sal as '工资' from emp as b inner join dept as c on c.deptno = b.deptno  
where b.sal>(select avg(a.sal) from emp as a where a.deptno = b.deptno) order by b.deptno;
+-----------+--------------+--------+--------+
| 部门号    | 部门名称     | 姓名   | 工资   |
+-----------+--------------+--------+--------+
| 1         | 事业部       | tom    | 2000   |
| 1         | 事业部       | biddy  | 2000   |
| 2         | 销售部       | jenny  | 1000   |
+-----------+--------------+--------+--------+
3 rows in set (0.00 sec)

select a.deptno as '部门号',count(a.sal) as '员工数' 
from emp as a where a.sal>(select avg(b.sal) from emp as b 
where a.deptno=b.deptno) group by a.deptno order by a.deptno;
+-----------+-----------+
| 部门号    | 员工数    |
+-----------+-----------+
| 1         |         2 |
| 2         |         1 |
+-----------+-----------+
2 rows in set (0.00 sec)

select a.deptno as '部门号',a.ename as '姓名',a.sal as '工资',
(select count(b.ename) from emp as b where b.sal<a.sal) as '人数' 
from emp as a where (select count(b.ename) from emp as b where b.sal<a.sal)>=5;
+-----------+--------+--------+--------+
| 部门号    | 姓名   | 工资   | 人数   |
+-----------+--------+--------+--------+
| 2         | pretty | 800    |      6 |
+-----------+--------+--------+--------+
1 row in set (0.00 sec)