mysql基础入门 动力节点[老杜]课堂作业

作业

1. 取得每个部门最高薪水的人员名称

第一步：取得每个部门最高薪水(按照部门编号分组，找出每一组最大值)

mysql> select deptno,max(sal) as maxsal from emp group by deptno;
+--------+---------+
| deptno | maxsal  |
+--------+---------+
|     10 | 5000.00 |
|     20 | 3000.00 |
|     30 | 2850.00 |
+--------+---------+

第二步：将以上的查询结果当做一张临时表 t，
t 和 emp 表连接，条件：t.deptno = e.deptno and t.maxsal = e.sal

select
e.ename, t.*
from
emp e
join
(select deptno,max(sal) as maxsal from emp group by deptno) t
on
t.deptno = e.deptno and t.maxsal = e.sal;

+-------+--------+---------+
| ename | deptno | maxsal  |
+-------+--------+---------+
| BLAKE |     30 | 2850.00 |
| SCOTT |     20 | 3000.00 |
| KING  |     10 | 5000.00 |
| FORD  |     20 | 3000.00 |
+-------+--------+---------+

2. 哪些人的薪水在部门的平均薪水之上

第一步：找出每个部门的平均薪水

select deptno,avg(sal) as avgsal from emp group by deptno;
+--------+-------------+
| deptno | avgsal      |
+--------+-------------+
|     10 | 2916.666667 |
|     20 | 2175.000000 |
|     30 | 1566.666667 |
+--------+-------------+

第二步：将以上查询结果当做 t 表，t 和 emp 表连接
条件：部门编号相同，并且 emp 的 sal 大于 t 表的 avgsal

select
t.*, e.ename, e.sal
from
emp e
join
(select deptno,avg(sal) as avgsal from emp group by deptno) t
on
e.deptno = t.deptno and e.sal > t.avgsal;
+--------+-------------+-------+---------+
| deptno | avgsal      | ename | sal     |
+--------+-------------+-------+---------+
|     30 | 1566.666667 | ALLEN | 1600.00 |
|     20 | 2175.000000 | JONES | 2975.00 |
|     30 | 1566.666667 | BLAKE | 2850.00 |
|     20 | 2175.000000 | SCOTT | 3000.00 |
|     10 | 2916.666667 | KING  | 5000.00 |
|     20 | 2175.000000 | FORD  | 3000.00 |
+--------+-------------+-------+---------+

3. 取得部门中（所有人的）平均的薪水等级

平均的薪水等级：先计算每一个薪水的等级，然后找出薪水等级的平均值。

平均薪水的等级：先计算平均薪水，然后找出每个平均薪水的等级值。

第一步：找出每个人的薪水等级
emp e 和 salgrade s 表连接。
连接条件：e.sal between s.losal and s.hisal

select
e.ename,e.sal,e.deptno,s.grade
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal;

+--------+---------+--------+-------+
| ename  | sal     | deptno | grade |
+--------+---------+--------+-------+
| CLARK  | 2450.00 |     10 |     4 |
| KING   | 5000.00 |     10 |     5 |
| MILLER | 1300.00 |     10 |     2 |

| SMITH  |  800.00 |     20 |     1 |
| ADAMS  | 1100.00 |     20 |     1 |
| SCOTT  | 3000.00 |     20 |     4 |
| FORD   | 3000.00 |     20 |     4 |
| JONES  | 2975.00 |     20 |     4 |

| MARTIN | 1250.00 |     30 |     2 |
| TURNER | 1500.00 |     30 |     3 |
| BLAKE  | 2850.00 |     30 |     4 |
| ALLEN  | 1600.00 |     30 |     3 |
| JAMES  |  950.00 |     30 |     1 |
| WARD   | 1250.00 |     30 |     2 |
+--------+---------+--------+-------+

第二步：基于以上的结果继续按照 deptno 分组，求 grade 的平均值。

select
e.deptno,avg(s.grade)
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal
group by
e.deptno;

+--------+--------------+
| deptno | avg(s.grade) |
+--------+--------------+
|     10 |       3.6667 |
|     20 |       2.8000 |
|     30 |       2.5000 |
+--------+--------------+

4. 不准用组函数（Max ），取得最高薪水

第一种：sal 降序，limit 1

select ename,sal from emp order by sal desc limit 1;
+-------+---------+
| ename | sal     |
+-------+---------+
| KING  | 5000.00 |
+-------+---------+

第二种方案：表的自连接

select sal from emp where sal not in
(select distinct a.sal
from emp a
join emp b
on a.sal < b.sal);
+---------+
| sal     |
+---------+
| 5000.00 |
+---------+

5. 取得平均薪水最高的部门的部门编号

第一种方案：降序取第一个。

第一步：找出每个部门的平均薪水

select deptno,avg(sal) as avgsal from emp group by deptno;
+--------+-------------+
| deptno | avgsal      |
+--------+-------------+
|     10 | 2916.666667 |
|     20 | 2175.000000 |
|     30 | 1566.666667 |
+--------+-------------+

第二步：降序选第一个。

select deptno,avg(sal) as avgsal from emp group by deptno order by avgsal desc limit 1;
+--------+-------------+
| deptno | avgsal      |
+--------+-------------+
|     10 | 2916.666667 |
+--------+-------------+

第二种方案：max

第一步：找出每个部门的平均薪水

select deptno,avg(sal) as avgsal from emp group by deptno;
+--------+-------------+
| deptno | avgsal      |
+--------+-------------+
|     10 | 2916.666667 |
|     20 | 2175.000000 |
|     30 | 1566.666667 |
+--------+-------------+

第二步：找出以上结果中 avgsal 最大的值。

select max(t.avgsal) from (select avg(sal) as avgsal from emp group by deptno) t;
+---------------+
| max(t.avgsal) |
+---------------+
|   2916.666667 |
+---------------+

第三步：

select
deptno,avg(sal) as avgsal
from
emp
group by
deptno
having
avgsal = (select max(t.avgsal) from (select avg(sal) as avgsal from emp group by deptno) t);

+--------+-------------+
| deptno | avgsal      |
+--------+-------------+
|     10 | 2916.666667 |
+--------+-------------+

6. 取得平均薪水最高的部门的部门名称

select
d.dname,avg(e.sal) as avgsal
from
emp e
join
dept d
on
e.deptno = d.deptno
group by
d.dname
order by
avgsal desc
limit
1;

+------------+-------------+
| dname      | avgsal      |
+------------+-------------+
| ACCOUNTING | 2916.666667 |
+------------+-------------+

7. 求平均薪水的等级最低的部门的部门名称

平均薪水是 800
平均薪水是 900
那么他俩都是 1 级别。

第一步：找出每个部门的平均薪水

select deptno,avg(sal) as avgsal from emp group by deptno;
+--------+-------------+
| deptno | avgsal      |
+--------+-------------+
|     10 | 2916.666667 |
|     20 | 2175.000000 |
|     30 | 1566.666667 |
+--------+-------------+

第二步：找出每个部门的平均薪水的等级
以上 t 表和 salgrade 表连接，条件：t.avgsal between s.losal and s.hisal

select
t.*,s.grade
from
(select d.dname,avg(sal) as avgsal from emp e join dept d on e.deptno = d.deptno group by d.dname) t
join
salgrade s
on
t.avgsal between s.losal and s.hisal;

+------------+-------------+-------+
| dname      | avgsal      | grade |
+------------+-------------+-------+
| SALES      | 1566.666667 |     3 |
| ACCOUNTING | 2916.666667 |     4 |
| RESEARCH   | 2175.000000 |     4 |
+------------+-------------+-------+

select
t.*,s.grade
from
(select d.dname,avg(sal) as avgsal from emp e join dept d on e.deptno = d.deptno group by d.dname) t
join
salgrade s
on
t.avgsal between s.losal and s.hisal
where
s.grade = (select grade from salgrade where (select avg(sal) as avgsal from emp group by deptno order by avgsal asc limit 1) between losal and hisal);

+-------+-------------+-------+
| dname | avgsal      | grade |
+-------+-------------+-------+
| SALES | 1566.666667 |     3 |
+-------+-------------+-------+

抛开之前的，最低等级你怎么着？

平均薪水最低的对应的等级一定是最低的.

select avg(sal) as avgsal from emp group by deptno order by avgsal asc limit 1;
+-------------+
| avgsal      |
+-------------+
| 1566.666667 |
+-------------+

select grade from salgrade where (select avg(sal) as avgsal from emp group by deptno order by avgsal asc limit 1) between losal and hisal;
+-------+
| grade |
+-------+
|     3 |
+-------+

8. 取得比普通员工(员工代码没有在 mgr 字段上出现的) 的最高薪水还要高的领导人姓名

比“普通员工的最高薪水”还要高的一定是领导！没毛病！！！！

mysql> select distinct mgr from emp where mgr is not null;
+------+
| mgr  |
+------+
| 7902 |
| 7698 |
| 7839 |
| 7566 |
| 7788 |
| 7782 |
+------+

员工编号没有在以上范围内的都是普通员工。

第一步：找出普通员工的最高薪水！
not in 在使用的时候，后面小括号中记得排除 NULL。

select max(sal) from emp where empno not in(select distinct mgr from emp where mgr is not null);
+----------+
| max(sal) |
+----------+
|  1600.00 |
+----------+

第二步：找出高于 1600 的

select ename,sal from emp where sal > (select max(sal) from emp where empno not in(select distinct mgr from emp where mgr is not null));
+-------+---------+
| ename | sal     |
+-------+---------+
| JONES | 2975.00 |
| BLAKE | 2850.00 |
| CLARK | 2450.00 |
| SCOTT | 3000.00 |
| KING  | 5000.00 |
| FORD  | 3000.00 |
+-------+---------+

9. 取得薪水最高的前五名员工

select ename,sal from emp order by sal desc limit 5;
+-------+---------+
| ename | sal     |
+-------+---------+
| KING  | 5000.00 |
| SCOTT | 3000.00 |
| FORD  | 3000.00 |
| JONES | 2975.00 |
| BLAKE | 2850.00 |
+-------+---------+

10. 取得薪水最高的第六到第十名员工

select ename,sal from emp order by sal desc limit 5, 5;
+--------+---------+
| ename  | sal     |
+--------+---------+
| CLARK  | 2450.00 |
| ALLEN  | 1600.00 |
| TURNER | 1500.00 |
| MILLER | 1300.00 |
| MARTIN | 1250.00 |
+--------+---------+

11. 取得最后入职的 5 名员工

日期也可以降序，升序。

select ename,hiredate from emp order by hiredate desc limit 5;

+--------+------------+
| ename  | hiredate   |
+--------+------------+
| ADAMS  | 1987-05-23 |
| SCOTT  | 1987-04-19 |
| MILLER | 1982-01-23 |
| FORD   | 1981-12-03 |
| JAMES  | 1981-12-03 |
+--------+------------+

12. 取得每个薪水等级有多少员工

分组 count

第一步：找出每个员工的薪水等级

select
e.ename,e.sal,s.grade
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal;
+--------+---------+-------+
| ename  | sal     | grade |
+--------+---------+-------+
| SMITH  |  800.00 |     1 |
| ALLEN  | 1600.00 |     3 |
| WARD   | 1250.00 |     2 |
| JONES  | 2975.00 |     4 |
| MARTIN | 1250.00 |     2 |
| BLAKE  | 2850.00 |     4 |
| CLARK  | 2450.00 |     4 |
| SCOTT  | 3000.00 |     4 |
| KING   | 5000.00 |     5 |
| TURNER | 1500.00 |     3 |
| ADAMS  | 1100.00 |     1 |
| JAMES  |  950.00 |     1 |
| FORD   | 3000.00 |     4 |
| MILLER | 1300.00 |     2 |
+--------+---------+-------+

第二步：继续按照 grade 分组统计数量

select
s.grade ,count(*)
from
emp e
join
salgrade s
on
e.sal between s.losal and s.hisal
group by
s.grade;

+-------+----------+
| grade | count(*) |
+-------+----------+
|     1 |        3 |
|     2 |        3 |
|     3 |        2 |
|     4 |        5 |
|     5 |        1 |
+-------+----------+

13. 面试题

有 3 个表 S（学生表），C（课程表），SC（学生选课表）

S（SNO，SNAME）代表（学号，姓名）

C（CNO，CNAME，CTEACHER）代表（课号，课名，教师）

SC（SNO，CNO，SCGRADE）代表（学号，课号，成绩）

问题：

• 找出没选过“黎明”老师的所有学生姓名。
• 列出 2 门以上（含 2 门）不及格学生姓名及平均成绩。
• 即学过 1 号课程又学过 2 号课所有学生的姓名。

14. 列出所有员工及其领导的姓名

select
a.ename '员工', b.ename '领导'
from
emp a
left join
emp b
on
a.mgr = b.empno;

+--------+-------+
| 员工   | 领导    |
+--------+-------+
| SMITH  | FORD  |
| ALLEN  | BLAKE |
| WARD   | BLAKE |
| JONES  | KING  |
| MARTIN | BLAKE |
| BLAKE  | KING  |
| CLARK  | KING  |
| SCOTT  | JONES |
| KING   | NULL  |
| TURNER | BLAKE |
| ADAMS  | SCOTT |
| JAMES  | BLAKE |
| FORD   | JONES |
| MILLER | CLARK |
+--------+-------+

15. 列出受雇日期早于其直接上级的所有员工的编号,姓名,部门名称

emp a 员工表
emp b 领导表
a.mgr = b.empno and a.hiredate < b.hiredate

select
a.ename '员工', a.hiredate, b.ename '领导', b.hiredate, d.dname
from
emp a
join
emp b
on
a.mgr = b.empno
join
dept d
on
a.deptno = d.deptno
where
a.hiredate < b.hiredate;

+-------+------------+-------+------------+------------+
| 员工  | hiredate   | 领导  | hiredate   | dname      |
+-------+------------+-------+------------+------------+
| SMITH | 1980-12-17 | FORD  | 1981-12-03 | RESEARCH   |
| ALLEN | 1981-02-20 | BLAKE | 1981-05-01 | SALES      |
| WARD  | 1981-02-22 | BLAKE | 1981-05-01 | SALES      |
| JONES | 1981-04-02 | KING  | 1981-11-17 | RESEARCH   |
| BLAKE | 1981-05-01 | KING  | 1981-11-17 | SALES      |
| CLARK | 1981-06-09 | KING  | 1981-11-17 | ACCOUNTING |
+-------+------------+-------+------------+------------+

16. 列出部门名称和这些部门的员工信息, 同时列出那些没有员工的部门

select
e.*,d.dname
from
emp e
right join
dept d
on
e.deptno = d.deptno;

+-------+--------+-----------+------+------------+---------+---------+--------+------------+
| EMPNO | ENAME  | JOB       | MGR  | HIREDATE   | SAL     | COMM    | DEPTNO | dname      |
+-------+--------+-----------+------+------------+---------+---------+--------+------------+
|  7782 | CLARK  | MANAGER   | 7839 | 1981-06-09 | 2450.00 |    NULL |     10 | ACCOUNTING |
|  7839 | KING   | PRESIDENT | NULL | 1981-11-17 | 5000.00 |    NULL |     10 | ACCOUNTING |
|  7934 | MILLER | CLERK     | 7782 | 1982-01-23 | 1300.00 |    NULL |     10 | ACCOUNTING |
|  7369 | SMITH  | CLERK     | 7902 | 1980-12-17 |  800.00 |    NULL |     20 | RESEARCH   |
|  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 | 2975.00 |    NULL |     20 | RESEARCH   |
|  7788 | SCOTT  | ANALYST   | 7566 | 1987-04-19 | 3000.00 |    NULL |     20 | RESEARCH   |
|  7876 | ADAMS  | CLERK     | 7788 | 1987-05-23 | 1100.00 |    NULL |     20 | RESEARCH   |
|  7902 | FORD   | ANALYST   | 7566 | 1981-12-03 | 3000.00 |    NULL |     20 | RESEARCH   |
|  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 | 1600.00 |  300.00 |     30 | SALES      |
|  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 | 1250.00 |  500.00 |     30 | SALES      |
|  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 | 1250.00 | 1400.00 |     30 | SALES      |
|  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 | 2850.00 |    NULL |     30 | SALES      |
|  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 | 1500.00 |    0.00 |     30 | SALES      |
|  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 |  950.00 |    NULL |     30 | SALES      |
|  NULL | NULL   | NULL      | NULL | NULL       |    NULL |    NULL |   NULL | OPERATIONS |
+-------+--------+-----------+------+------------+---------+---------+--------+------------+

17. 列出至少有 5 个员工的所有部门

按照部门编号分组，计数，筛选出 >= 5

select
deptno
from
emp
group by
deptno
having
count(*) >= 5;

+--------+
| deptno |
+--------+
|     20 |
|     30 |
+--------+

18. 列出薪金比"SMITH" 多的所有员工信息

select ename,sal from emp where sal > (select sal from emp where ename = 'SMITH');
+--------+---------+
| ename  | sal     |
+--------+---------+
| ALLEN  | 1600.00 |
| WARD   | 1250.00 |
| JONES  | 2975.00 |
| MARTIN | 1250.00 |
| BLAKE  | 2850.00 |
| CLARK  | 2450.00 |
| SCOTT  | 3000.00 |
| KING   | 5000.00 |
| TURNER | 1500.00 |
| ADAMS  | 1100.00 |
| JAMES  |  950.00 |
| FORD   | 3000.00 |
| MILLER | 1300.00 |
+--------+---------+

19. 列出所有"CLERK"( 办事员) 的姓名及其部门名称, 部门的人数

select ename,job from emp where job = 'CLERK';
+--------+-------+
| ename  | job   |
+--------+-------+
| SMITH  | CLERK |
| ADAMS  | CLERK |
| JAMES  | CLERK |
| MILLER | CLERK |
+--------+-------+

select
e.ename,e.job,d.dname
from
emp e
join
dept d
on
e.deptno = d.deptno
where
e.job = 'CLERK';

+--------+-------+------------+
| ename  | job   | dname      |
+--------+-------+------------+
| MILLER | CLERK | ACCOUNTING |
| SMITH  | CLERK | RESEARCH   |
| ADAMS  | CLERK | RESEARCH   |
| JAMES  | CLERK | SALES      |
+--------+-------+------------+

select
e.ename,e.job,d.dname,d.deptno
from
emp e
join
dept d
on
e.deptno = d.deptno
where
e.job = 'CLERK';

+--------+-------+------------+--------+
| ename  | job   | dname      | deptno |
+--------+-------+------------+--------+
| MILLER | CLERK | ACCOUNTING |     10 |
| SMITH  | CLERK | RESEARCH   |     20 |
| ADAMS  | CLERK | RESEARCH   |     20 |
| JAMES  | CLERK | SALES      |     30 |
+--------+-------+------------+--------+


//每个部门的人数？
select deptno, count(*) as deptcount from emp group by deptno;
+--------+-----------+
| deptno | deptcount |
+--------+-----------+
|     10 |         3 |
|     20 |         5 |
|     30 |         6 |
+--------+-----------+

select
t1.*,t2.deptcount
from
(select
e.ename,e.job,d.dname,d.deptno
from
emp e
join
dept d
on
e.deptno = d.deptno
where
e.job = 'CLERK') t1
join
(select deptno, count(*) as deptcount from emp group by deptno) t2
on
t1.deptno = t2.deptno;

+--------+-------+------------+--------+-----------+
| ename  | job   | dname      | deptno | deptcount |
+--------+-------+------------+--------+-----------+
| MILLER | CLERK | ACCOUNTING |     10 |         3 |
| SMITH  | CLERK | RESEARCH   |     20 |         5 |
| ADAMS  | CLERK | RESEARCH   |     20 |         5 |
| JAMES  | CLERK | SALES      |     30 |         6 |
+--------+-------+------------+--------+-----------+

20. 列出最低薪金大于 1500 的各种工作及从事此工作的全部雇员人数

按照工作岗位分组求最小值。

select job,count(*) from emp group by job having min(sal) > 1500;

+-----------+----------+
| job       | count(*) |
+-----------+----------+
| ANALYST   |        2 |
| MANAGER   |        3 |
| PRESIDENT |        1 |
+-----------+----------+

21. 列出在部门"SALES"< 销售部> 工作的员工的姓名, 假定不知道销售部的部门编号.

select ename from emp where deptno = (select deptno from dept where dname = 'SALES');

+--------+
| ename  |
+--------+
| ALLEN  |
| WARD   |
| MARTIN |
| BLAKE  |
| TURNER |
| JAMES  |
+--------+

22. 列出薪金高于公司平均薪金的所有员工, 所在部门, 上级领导, 雇员的工资等级.

select
e.ename '员工',d.dname,l.ename '领导',s.grade
from
emp e
join
dept d
on
e.deptno = d.deptno
left join
emp l
on
e.mgr = l.empno
join
salgrade s
on
e.sal between s.losal and s.hisal
where
e.sal > (select avg(sal) from emp);


+-------+------------+-------+-------+
| 员工  | dname      | 领导   | grade |
+-------+------------+-------+-------+
| JONES | RESEARCH   | KING  |     4 |
| BLAKE | SALES      | KING  |     4 |
| CLARK | ACCOUNTING | KING  |     4 |
| SCOTT | RESEARCH   | JONES |     4 |
| KING  | ACCOUNTING | NULL  |     5 |
| FORD  | RESEARCH   | JONES |     4 |
+-------+------------+-------+-------+

23. 列出与"SCOTT" 从事相同工作的所有员工及部门名称

select job from emp where ename = 'SCOTT';
+---------+
| job     |
+---------+
| ANALYST |
+---------+

select
e.ename,e.job,d.dname
from
emp e
join
dept d
on
e.deptno = d.deptno
where
e.job = (select job from emp where ename = 'SCOTT')
and
e.ename <> 'SCOTT';

+-------+---------+----------+
| ename | job     | dname    |
+-------+---------+----------+
| FORD  | ANALYST | RESEARCH |
+-------+---------+----------+

24. 列出薪金等于部门 30 中员工的薪金的其他员工的姓名和薪金.

select distinct sal from emp where deptno = 30;
+---------+
| sal     |
+---------+
| 1600.00 |
| 1250.00 |
| 2850.00 |
| 1500.00 |
|  950.00 |
+---------+

select
ename,sal
from
emp
where
sal in(select distinct sal from emp where deptno = 30)
and
deptno <> 30;

Empty set (0.00 sec)

25. 列出薪金高于在部门 30 工作的，员工薪金的姓名·薪金·部门名称

select max(sal) from emp where deptno = 30;
+----------+
| max(sal) |
+----------+
|  2850.00 |
+----------+

select
e.ename,e.sal,d.dname
from
emp e
join
dept d
on
e.deptno = d.deptno
where
e.sal > (select max(sal) from emp where deptno = 30);

+-------+---------+------------+
| ename | sal     | dname      |
+-------+---------+------------+
| KING  | 5000.00 | ACCOUNTING |
| JONES | 2975.00 | RESEARCH   |
| SCOTT | 3000.00 | RESEARCH   |
| FORD  | 3000.00 | RESEARCH   |
+-------+---------+------------+

26. 列出在每个部门工作的员工数量, 平均工资和平均服务期限

没有员工的部门，部门人数是 0

select
d.deptno, count(e.ename) ecount,ifnull(avg(e.sal),0) as avgsal, ifnull(avg(timestampdiff(YEAR, hiredate, now())), 0) as avgservicetime
from
emp e
right join
dept d
on
e.deptno = d.deptno
group by
d.deptno;

+--------+--------+-------------+----------------+
| deptno | ecount | avgsal      | avgservicetime |
+--------+--------+-------------+----------------+
|     10 |      3 | 2916.666667 |        38.0000 |
|     20 |      5 | 2175.000000 |        35.8000 |
|     30 |      6 | 1566.666667 |        38.3333 |
|     40 |      0 |    0.000000 |         0.0000 |
+--------+--------+-------------+----------------+

在 mysql 当中怎么计算两个日期的“年差”，差了多少年？
TimeStampDiff(间隔类型, 前一个日期, 后一个日期)

timestampdiff(YEAR, hiredate, now())

间隔类型：
SECOND 秒，
MINUTE 分钟，
HOUR 小时，
DAY 天，
WEEK 星期
MONTH 月，
QUARTER 季度，
YEAR 年

27. 列出所有员工的姓名、部门名称和工资

select
e.ename,d.dname,e.sal
from
emp e
join
dept d
on
e.deptno = d.deptno;

+--------+------------+---------+
| ename  | dname      | sal     |
+--------+------------+---------+
| CLARK  | ACCOUNTING | 2450.00 |
| KING   | ACCOUNTING | 5000.00 |
| MILLER | ACCOUNTING | 1300.00 |
| SMITH  | RESEARCH   |  800.00 |
| JONES  | RESEARCH   | 2975.00 |
| SCOTT  | RESEARCH   | 3000.00 |
| ADAMS  | RESEARCH   | 1100.00 |
| FORD   | RESEARCH   | 3000.00 |
| ALLEN  | SALES      | 1600.00 |
| WARD   | SALES      | 1250.00 |
| MARTIN | SALES      | 1250.00 |
| BLAKE  | SALES      | 2850.00 |
| TURNER | SALES      | 1500.00 |
| JAMES  | SALES      |  950.00 |
+--------+------------+---------+

28. 列出所有部门的详细信息和人数

select
d.deptno,d.dname,d.loc,count(e.ename)
from
emp e
right join
dept d
on
e.deptno = d.deptno
group by
d.deptno,d.dname,d.loc;

+--------+------------+----------+----------------+
| deptno | dname      | loc      | count(e.ename) |
+--------+------------+----------+----------------+
|     10 | ACCOUNTING | NEW YORK |              3 |
|     20 | RESEARCH   | DALLAS   |              5 |
|     30 | SALES      | CHICAGO  |              6 |
|     40 | OPERATIONS | BOSTON   |              0 |
+--------+------------+----------+----------------+

29. 列出各种工作的最低工资及从事此工作的雇员姓名

select
job,min(sal) as minsal
from
emp
group by
job;

+-----------+----------+
| job       | minsal   |
+-----------+----------+
| ANALYST   |  3000.00 |
| CLERK     |   800.00 |
| MANAGER   |  2450.00 |
| PRESIDENT |  5000.00 |
| SALESMAN  |  1250.00 |
+-----------+----------+

emp e 和以上 t 连接

select
e.ename,t.*
from
emp e
join
(select
job,min(sal) as minsal
from
emp
group by
job) t
on
e.job = t.job and e.sal = t.minsal;

+--------+-----------+---------+
| ename  | job       | minsal  |
+--------+-----------+---------+
| SMITH  | CLERK     |  800.00 |
| WARD   | SALESMAN  | 1250.00 |
| MARTIN | SALESMAN  | 1250.00 |
| CLARK  | MANAGER   | 2450.00 |
| SCOTT  | ANALYST   | 3000.00 |
| KING   | PRESIDENT | 5000.00 |
| FORD   | ANALYST   | 3000.00 |
+--------+-----------+---------+

30. 列出各个部门的 MANAGER(领导) 的最低薪金

select
deptno, min(sal)
from
emp
where
job = 'MANAGER'
group by
deptno;

+--------+----------+
| deptno | min(sal) |
+--------+----------+
|     10 |  2450.00 |
|     20 |  2975.00 |
|     30 |  2850.00 |
+--------+----------+

31. 列出所有员工的 年工资, 按 年薪从低到高排序

select
ename,(sal + ifnull(comm,0)) * 12 as yearsal
from
emp
order by
yearsal asc;

+--------+----------+
| ename  | yearsal  |
+--------+----------+
| SMITH  |  9600.00 |
| JAMES  | 11400.00 |
| ADAMS  | 13200.00 |
| MILLER | 15600.00 |
| TURNER | 18000.00 |
| WARD   | 21000.00 |
| ALLEN  | 22800.00 |
| CLARK  | 29400.00 |
| MARTIN | 31800.00 |
| BLAKE  | 34200.00 |
| JONES  | 35700.00 |
| FORD   | 36000.00 |
| SCOTT  | 36000.00 |
| KING   | 60000.00 |
+--------+----------+

32. 求出员工领导的薪水超过 3000 的员工名称与领导

select
a.ename '员工',b.ename '领导'
from
emp a
join
emp b
on
a.mgr = b.empno
where
b.sal > 3000;

+-------+------+
| 员工  | 领导   |
+-------+------+
| JONES | KING |
| BLAKE | KING |
| CLARK | KING |
+-------+------+

33. 求出部门名称中, 带’S’字符的部门员工的工资合计、部门人数

select
d.deptno,d.dname,d.loc,count(e.ename),ifnull(sum(e.sal),0) as sumsal
from
emp e
right join
dept d
on
e.deptno = d.deptno
where
d.dname like '%S%'
group by
d.deptno,d.dname,d.loc;

+--------+------------+---------+----------------+----------+
| deptno | dname      | loc     | count(e.ename) | sumsal   |
+--------+------------+---------+----------------+----------+
|     20 | RESEARCH   | DALLAS  |              5 | 10875.00 |
|     30 | SALES      | CHICAGO |              6 |  9400.00 |
|     40 | OPERATIONS | BOSTON  |              0 |     0.00 |
+--------+------------+---------+----------------+----------+

34. 给任职日期超过 30 年的员工加薪 10%.

update emp set sal = sal * 1.1 where timestampdiff(YEAR, hiredate, now()) > 30;