MySQL练习题

练习题

(1)、取得每个部门最高薪水的人员名称

第一步: 取每个部门最高薪水

mysql> select deptno,max(sal) from EMP group by deptno;
+--------+----------+
| deptno | max(sal) |
+--------+----------+
|     10 |     5000 |
|     20 |     3000 |
|     30 |     2850 |
+--------+----------+
3 rows in set (0.00 sec)

第二步:将以上的结果当做临时表t,t表盒emp_e表进行连接,条件是:t.deptno = e.deptno and t.maxsal axsal = e.sal

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

mysql> select e.ename,t.* from (select deptno,max(sal)as maxsal from EMP group by deptno) t join EMP e  on t.deptno = e.deptnno and t.maxsal = e.sal;
+-------+--------+--------+
| ename | deptno | maxsal |
+-------+--------+--------+
| BLAKE |     30 |   2850 |
| SCOTT |     20 |   3000 |
| KING  |     10 |   5000 |
| FORD  |     20 |   3000 |
+-------+--------+--------+
4 rows in set (0.00 sec)

(2)、那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

mysql> select avg(sal),deptno from EMP group by deptno;
+--------------------+--------+
| avg(sal)           | deptno |
+--------------------+--------+
| 2916.6666666666665 |     10 |
|               2175 |     20 |
| 1566.6666666666667 |     30 |
+--------------------+--------+
3 rows in set (0.00 sec)

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

mysql> select t.*,e.ename,e.sal
    -> from EMP e
    -> join (select avg(sal) as avgsal,deptno from EMP group by deptno) t
    -> on e.deptno = t.deptno and e.sal > t.avgsal;
+--------------------+--------+-------+------+
| avgsal             | deptno | ename | sal  |
+--------------------+--------+-------+------+
| 1566.6666666666667 |     30 | ALLEN | 1600 |
|               2175 |     20 | JONES | 2975 |
| 1566.6666666666667 |     30 | BLAKE | 2850 |
|               2175 |     20 | SCOTT | 3000 |
| 2916.6666666666665 |     10 | KING  | 5000 |
|               2175 |     20 | FORD  | 3000 |
+--------------------+--------+-------+------+
6 rows in set (0.00 sec)

(3)、取得部门中(所有人)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数
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 salgrade s表连接
连接条件: e.sal between s.losal and s.hisal

mysql> 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 |
+--------+------+--------+-------+
| SMITH  |  800 |     20 |     1 |
| ALLEN  | 1600 |     30 |     3 |
| WARD   | 1250 |     30 |     2 |
| JONES  | 2975 |     20 |     4 |
| MARTIN | 1250 |     30 |     2 |
| BLAKE  | 2850 |     30 |     4 |
| CLARK  | 2450 |     10 |     4 |
| SCOTT  | 3000 |     20 |     4 |
| KING   | 5000 |     10 |     5 |
| TURNER | 1500 |     30 |     3 |
| ADAMS  | 1100 |     20 |     1 |
| JAMES  |  950 |     30 |     1 |
| FORD   | 3000 |     20 |     4 |
| MILLER | 1300 |     10 |     2 |
+--------+------+--------+-------+
14 rows in set (0.00 sec)

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 |
+--------+--------------+
3 rows in set (0.00 sec)

(4)、不准用组函数(MAX), 取得最高薪资

第一种:sal 降序,limit 1

mysql> select * from EMP order by sal desc limit 1;
+-------+-------+-----------+------+------------+------+------+--------+
| EMPNO | ENAME | JOB       | MGR  | HIREDATE   | SAL  | COMM | DEPTNO |
+-------+-------+-----------+------+------------+------+------+--------+
|  7839 | KING  | PRESIDENT | NULL | 1981-11-17 | 5000 | NULL |     10 |
+-------+-------+-----------+------+------------+------+------+--------+
1 row in set (0.00 sec)

第二种:select max(sal) from emp;

第三种:表的自连接

mysql> 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 |
+------+
1 row in set (0.01 sec)

(5)、取得平均薪水最高的部门的部门编号

第一种方案:降序选第一个
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 | 2916.6666666666665 |
|     20 |               2175 |
|     30 | 1566.6666666666667 |
+--------+--------------------+
3 rows in set (0.00 sec)

第二步:降序选第一个

mysql> select deptno,avg(sal) as avgsal from EMP group by deptno order by avgsal desc limit 1;
+--------+--------------------+
| deptno | avgsal             |
+--------+--------------------+
|     10 | 2916.6666666666665 |
+--------+--------------------+
1 row in set (0.00 sec)

(6)、取得平均薪水最高的部门的部门名称

mysql> select deptno,avg(sal) as avgsal from EMP e group by deptno order by avgsal desc  limit 1;
+--------+--------------------+
| deptno | avgsal             |
+--------+--------------------+
|     10 | 2916.6666666666665 |
+--------+--------------------+
1 row in set (0.01 sec)

(7)、求平均薪水的等级最低的部门的部门名称

先查出最每个部门平均的薪水

mysql> select deptno,avg(sal) from EMP group by deptno;
+--------+--------------------+
| deptno | avg(sal)           |
+--------+--------------------+
|     10 | 2916.6666666666665 |
|     20 |               2175 |
|     30 | 1566.6666666666667 |
+--------+--------------------+
3 rows in set (0.00 sec)

找出每个部门的平均薪水的等级 然后在和salgrade表连接 :条件t.avgsal between s.losal and s.hisal

mysql> select t.*,s.grade 
    -> from 
    ->   (select dname,avg(sal)  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 |
+------------+--------------------+-------+
| ACCOUNTING | 2916.6666666666665 |     4 |
| RESEARCH   |               2175 |     4 |
| SALES      | 1566.6666666666667 |     3 |
+------------+--------------------+-------+
3 rows in set (0.00 sec)

找出平均薪水最低的对应的等级一定是最低的

mysql> select avg(sal) as avgsal from EMP group by deptno order by avgsal asc limit 1 ;
+--------------------+
| avgsal             |
+--------------------+
| 1566.6666666666667 |
+--------------------+
1 row in set (0.00 sec)

结果

mysql>  select t.*,s.grade  from                                                                                            
    -> (select dname,avg(sal)  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 | 1566.6666666666667 |     3 |
+-------+--------------------+-------+
1 row in set (0.00 sec)

(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

第一步:找出普通员工的最高薪水
not in 在使用的时候,需要手动排除 null值

mysql> select max(sal) from EMP where empno not in(select distinct mgr from EMP where mgr is not null);
+----------+
| max(sal) |
+----------+
|     1600 |
+----------+
1 row in set (0.00 sec)

第二步找出高于1600的工资

mysql> 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 |
| BLAKE | 2850 |
| CLARK | 2450 |
| SCOTT | 3000 |
| KING  | 5000 |
| FORD  | 3000 |
+-------+------+
6 rows in set (0.00 sec)

(9)、取得薪水最高的前五名员工

mysql> select ename,sal from EMP order by sal desc limit 5;
+-------+------+
| ename | sal  |
+-------+------+
| KING  | 5000 |
| FORD  | 3000 |
| SCOTT | 3000 |
| JONES | 2975 |
| BLAKE | 2850 |
+-------+------+
5 rows in set (0.00 sec)

(10)、取得薪水最高的六到第十名

mysql> select ename,sal from EMP  order by sal desc limit 5,5;
+--------+------+
| ename  | sal  |
+--------+------+
| CLARK  | 2450 |
| ALLEN  | 1600 |
| TURNER | 1500 |
| MILLER | 1300 |
| WARD   | 1250 |
+--------+------+
5 rows in set (0.00 sec)

(11)、取得最后入职的5名员工

mysql> select * from EMP order by HIREDATE desc limit 5 ;
+-------+--------+---------+------+------------+------+------+--------+
| EMPNO | ENAME  | JOB     | MGR  | HIREDATE   | SAL  | COMM | DEPTNO |
+-------+--------+---------+------+------------+------+------+--------+
|  7788 | SCOTT  | ANALYST | 7566 | 1987-07-13 | 3000 | NULL |     20 |
|  7876 | ADAMS  | CLERK   | 7788 | 1987-07-13 | 1100 | NULL |     20 |
|  7934 | MILLER | CLERK   | 7782 | 1982-01-23 | 1300 | NULL |     10 |
|  7900 | JAMES  | CLERK   | 7698 | 1981-12-03 |  950 | NULL |     30 |
|  7902 | FORD   | ANALYST | 7566 | 1981-12-03 | 3000 | NULL |     20 |
+-------+--------+---------+------+------------+------+------+--------+
5 rows in set (0.00 sec)

(12)、取得每个薪水 等级有多少个员工

第一步:找出每个员工的薪水等级

mysql> 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 |     1 |
| ALLEN  | 1600 |     3 |
| WARD   | 1250 |     2 |
| JONES  | 2975 |     4 |
| MARTIN | 1250 |     2 |
| BLAKE  | 2850 |     4 |
| CLARK  | 2450 |     4 |
| SCOTT  | 3000 |     4 |
| KING   | 5000 |     5 |
| TURNER | 1500 |     3 |
| ADAMS  | 1100 |     1 |
| JAMES  |  950 |     1 |
| FORD   | 3000 |     4 |
| MILLER | 1300 |     2 |
+--------+------+-------+
14 rows in set (0.00 sec)

结果

mysql> 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 |
+-------+----------+
5 rows in set (0.00 sec)

(13)、取得

(14)、列出所有员工及领导的姓名

mysql> select a.ename "员工",b.ename "领导" from EMP a 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  |
| TURNER | BLAKE  |
| ADAMS  | SCOTT  |
| JAMES  | BLAKE  |
| FORD   | JONES  |
| MILLER | CLARK  |
+--------+--------+
13 rows in set (0.00 sec)

(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",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
and a.hiredate < b.hiredate
+--------+--------+------------+------------+
| 员工   | 领导   | hiredate   | dname      |
+--------+--------+------------+------------+
| CLARK  | KING   | 1981-11-17 | ACCOUNTING |
| SMITH  | FORD   | 1981-12-03 | RESEARCH   |
| JONES  | KING   | 1981-11-17 | RESEARCH   |
| ALLEN  | BLAKE  | 1981-05-01 | SALES      |
| WARD   | BLAKE  | 1981-05-01 | SALES      |
| BLAKE  | KING   | 1981-11-17 | SALES      |
+--------+--------+------------+------------+
6 rows in set (0.00 sec)

(16)、列出部门名称和这些部门的员工信息，同时列出哪些没有员工的部门

emp e
dept d

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 | NULL |     10 | ACCOUNTING |
|  7839 | KING   | PRESIDENT | NULL | 1981-11-17 | 5000 | NULL |     10 | ACCOUNTING |
|  7934 | MILLER | CLERK     | 7782 | 1982-01-23 | 1300 | NULL |     10 | ACCOUNTING |
|  7369 | SMITH  | CLERK     | 7902 | 1980-12-17 |  800 | NULL |     20 | RESEARCH   |
|  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 | 2975 | NULL |     20 | RESEARCH   |
|  7788 | SCOTT  | ANALYST   | 7566 | 1987-07-13 | 3000 | NULL |     20 | RESEARCH   |
|  7876 | ADAMS  | CLERK     | 7788 | 1987-07-13 | 1100 | NULL |     20 | RESEARCH   |
|  7902 | FORD   | ANALYST   | 7566 | 1981-12-03 | 3000 | NULL |     20 | RESEARCH   |
|  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 | 1600 |  300 |     30 | SALES      |
|  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 | 1250 |  500 |     30 | SALES      |
|  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 | 1250 | 1400 |     30 | SALES      |
|  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 | 2850 | NULL |     30 | SALES      |
|  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 | 1500 |    0 |     30 | SALES      |
|  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 |  950 | NULL |     30 | SALES      |
|  NULL | NULL   | NULL      | NULL | NULL       | NULL | NULL |   NULL | OPERATIONS |
+-------+--------+-----------+------+------------+------+------+--------+------------+
15 rows in set (0.00 sec)

(17)、列出至少有五个员工的所有部门

mysql> select deptno,count(deptno) from EMP group by deptno having count(deptno)>=5;
+--------+---------------+
| deptno | count(deptno) |
+--------+---------------+
|     20 |             5 |
|     30 |             6 |
+--------+---------------+
2 rows in set (0.00 sec)

(18)、列出薪金比"SMITH"多的所有员工信息

mysql>  select * from EMP where sal >(select sal from EMP where ename="SMITH");
+-------+--------+-----------+------+------------+------+------+--------+
| EMPNO | ENAME  | JOB       | MGR  | HIREDATE   | SAL  | COMM | DEPTNO |
+-------+--------+-----------+------+------------+------+------+--------+
|  7499 | ALLEN  | SALESMAN  | 7698 | 1981-02-20 | 1600 |  300 |     30 |
|  7521 | WARD   | SALESMAN  | 7698 | 1981-02-22 | 1250 |  500 |     30 |
|  7566 | JONES  | MANAGER   | 7839 | 1981-04-02 | 2975 | NULL |     20 |
|  7654 | MARTIN | SALESMAN  | 7698 | 1981-09-28 | 1250 | 1400 |     30 |
|  7698 | BLAKE  | MANAGER   | 7839 | 1981-05-01 | 2850 | NULL |     30 |
|  7782 | CLARK  | MANAGER   | 7839 | 1981-06-09 | 2450 | NULL |     10 |
|  7788 | SCOTT  | ANALYST   | 7566 | 1987-07-13 | 3000 | NULL |     20 |
|  7839 | KING   | PRESIDENT | NULL | 1981-11-17 | 5000 | NULL |     10 |
|  7844 | TURNER | SALESMAN  | 7698 | 1981-09-08 | 1500 |    0 |     30 |
|  7876 | ADAMS  | CLERK     | 7788 | 1987-07-13 | 1100 | NULL |     20 |
|  7900 | JAMES  | CLERK     | 7698 | 1981-12-03 |  950 | NULL |     30 |
|  7902 | FORD   | ANALYST   | 7566 | 1981-12-03 | 3000 | NULL |     20 |
|  7934 | MILLER | CLERK     | 7782 | 1982-01-23 | 1300 | NULL |     10 |
+-------+--------+-----------+------+------------+------+------+--------+
13 rows in set (0.00 sec)

(19)、列出所有"CLERK"(办事员)的姓名及其姓名,部门的人数

mysql> 
select 
      e.ename,e.job 
from 
      EMP e
join      
      DEPT d
on 
      e.deptno = d.deptno
where 
      e.JOB ="CLERK";

找出部门人数

mysql> select deptno,count(*)as dptcount from EMP group by deptno;
+--------+----------+
| deptno | dptcount |
+--------+----------+
|     10 |        3 |
|     20 |        5 |
|     30 |        6 |
+--------+----------+
3 rows in set (0.00 sec)
```sql
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 |
+--------+-------+------------+--------+-----------+
| SMITH  | CLERK | RESEARCH   |     20 |         5 |
| ADAMS  | CLERK | RESEARCH   |     20 |         5 |
| JAMES  | CLERK | SALES      |     30 |         6 |
| MILLER | CLERK | ACCOUNTING |     10 |         3 |
+--------+-------+------------+--------+-----------+

(20)、列出最低薪资大与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

mysql> select job,count(*) from EMP group by job having min(sal) >1500;
+-----------+----------+
| job       | count(*) |
+-----------+----------+
| ANALYST   |        2 |
| MANAGER   |        3 |
| PRESIDENT |        1 |
+-----------+----------+
3 rows in set (0.00 sec)

(21)、列出部门"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

mysql> 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

mysql> select e.ename "员工",d.dname,a.ename "领导",s.grade
    -> from EMP e
    -> join DEPT d
    -> on e.deptno = d.deptno
    -> left join EMP a
    -> on e.mgr = a.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 |
+--------+------------+--------+-------+
6 rows in set (0.00 sec)

(23)、列出与"SCOTT" 从事相同工作的所有员工及部门名称

mysql> 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 enname="SCOTT") and e.ename <>"SCOTT";
+-------+---------+----------+
| ename | job     | dname    |
+-------+---------+----------+
| FORD  | ANALYST | RESEARCH |
+-------+---------+----------+
1 row in set (0.00 sec)

(24)、列出薪金等于部门30中员工的薪金的其他员工的姓名的薪金

mysql> select ename,sal from EMP where sal in (select sal from EMP e where deptno = 30) and deptno <> 30;

(25)、列出薪金高于在部门 30工作的所有员工的薪金的员工姓名和薪金

mysql> select max(sal) from EMP where deptno =30;
+----------+
| max(sal) |
+----------+
|     2850 |
+----------+
1 row in set (0.00 sec)
mysql> select  e.ename ,e.sal ,d.dname from  EMP e join DEPT d on e.deptno=d.deptno where sal >(select max(sal) from EMP where deptno =30);
+-------+------+------------+
| ename | sal  | dname      |
+-------+------+------------+
| JONES | 2975 | RESEARCH   |
| SCOTT | 3000 | RESEARCH   |
| KING  | 5000 | ACCOUNTING |
| FORD  | 3000 | RESEARCH   |
+-------+------+------------+
4 rows in set (0.00 sec)

(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

mysql> select d.*,count(e.ename) from EMP e right join DEPT d on d.deptno = e.deptno group by d.deptno;
+--------+------------+----------+----------------+
| DEPTNO | DNAME      | LOC      | count(e.ename) |
+--------+------------+----------+----------------+
|     10 | ACCOUNTING | NEW YORK |              3 |
|     20 | RESEARCH   | DALLAS   |              5 |
|     30 | SALES      | CHICAGO  |              6 |
|     40 | OPERATIONS | BOSTON   |              0 |
+--------+------------+----------+----------------+
4 rows in set (0.00 sec)

mysql> select d.*,count(e.ename),avg(sal),avg(timestampdiff(YEAR,hiredate,now())) as time from EMP e right join DEPT d on d.deptno = e.deptno group by d.deptno;
+--------+------------+----------+----------------+--------------------+---------+
| DEPTNO | DNAME      | LOC      | count(e.ename) | avg(sal)           | time    |
+--------+------------+----------+----------------+--------------------+---------+
|     10 | ACCOUNTING | NEW YORK |              3 | 2916.6666666666665 | 38.3333 |
|     20 | RESEARCH   | DALLAS   |              5 |               2175 | 36.4000 |
|     30 | SALES      | CHICAGO  |              6 | 1566.6666666666667 | 38.5000 |
|     40 | OPERATIONS | BOSTON   |              0 |               NULL |    NULL |
+--------+------------+----------+----------------+--------------------+---------+
4 rows in set (0.00 sec)

(27)、列出所有员工的姓名、部门名称和工资

mysql> select e.ename,d.dname,e.sal from EMP e join DEPT d on e.deptno=d.deptno
    -> ;
+--------+------------+------+
| ename  | dname      | sal  |
+--------+------------+------+
| CLARK  | ACCOUNTING | 2450 |
| KING   | ACCOUNTING | 5000 |
| MILLER | ACCOUNTING | 1300 |
| SMITH  | RESEARCH   |  800 |
| JONES  | RESEARCH   | 2975 |
| SCOTT  | RESEARCH   | 3000 |
| ADAMS  | RESEARCH   | 1100 |
| FORD   | RESEARCH   | 3000 |
| ALLEN  | SALES      | 1600 |
| WARD   | SALES      | 1250 |
| MARTIN | SALES      | 1250 |
| BLAKE  | SALES      | 2850 |
| TURNER | SALES      | 1500 |
| JAMES  | SALES      |  950 |
+--------+------------+------+
14 rows in set (0.00 sec)

(28)、列出所有员工的详细信息和人数

mysql> select d.deptno ,d.dname,d.loc from EMP e join DEPT d on e.deptno = d.deptno group by d.deptno ,d.dname,d.loc;
+--------+------------+----------+
| deptno | dname      | loc      |
+--------+------------+----------+
|     10 | ACCOUNTING | NEW YORK |
|     20 | RESEARCH   | DALLAS   |
|     30 | SALES      | CHICAGO  |
+--------+------------+----------+
3 rows in set (0.00 sec)

(29)、列出各种工作的最低工资及其从事此工作的雇员姓名

mysql> select e.ename,t.* from EMP e join (select job,min(sal) as sal from EMP group by job) t on e.job=t.job and e.sal = t.sal;
+--------+-----------+------+
| ename  | job       | sal  |
+--------+-----------+------+
| SMITH  | CLERK     |  800 |
| WARD   | SALESMAN  | 1250 |
| MARTIN | SALESMAN  | 1250 |
| CLARK  | MANAGER   | 2450 |
| SCOTT  | ANALYST   | 3000 |
| KING   | PRESIDENT | 5000 |
| FORD   | ANALYST   | 3000 |
+--------+-----------+------+
7 rows in set (0.00 sec)

(30)、列出各个部门的MANAGER()领导的最低工资

mysql> select deptno,min(sal) from EMP where job='MANAGER' group by deptno;
+--------+----------+
| deptno | min(sal) |
+--------+----------+
|     10 |     2450 |
|     20 |     2975 |
|     30 |     2850 |
+--------+----------+
3 rows in set (0.00 sec)

(31)、列出所有员工的年工资,按年薪从低到高排序

mysql> select ename,(sal+ ifnull(comm,0))*12 as yearsal from EMP order by yearsal asc;
+--------+---------+
| ename  | yearsal |
+--------+---------+
| SMITH  |    9600 |
| JAMES  |   11400 |
| ADAMS  |   13200 |
| MILLER |   15600 |
| TURNER |   18000 |
| WARD   |   21000 |
| ALLEN  |   22800 |
| CLARK  |   29400 |
| MARTIN |   31800 |
| BLAKE  |   34200 |
| JONES  |   35700 |
| SCOTT  |   36000 |
| FORD   |   36000 |
| KING   |   60000 |
+--------+---------+
14 rows in set (0.00 sec)

(32)、求出员工领导的薪水超过3000 的员工名称与领导

mysql> select  a.ename "员工",a.sal,b.ename "领导",b.sal from EMP a join EMP  b on a.mgr=b.empno where b.sal >3000;
+--------+------+--------+------+
| 员工   | sal  | 领导   | sal  |
+--------+------+--------+------+
| JONES  | 2975 | KING   | 5000 |
| BLAKE  | 2850 | KING   | 5000 |
| CLARK  | 2450 | KING   | 5000 |
+--------+------+--------+------+
3 rows in set (0.00 sec)

(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，

mysql> select d.deptno,d.dname,d.loc,count(e.ename),ifnull(sum(e.sal),0) 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) | ifnull(sum(e.sal),0) |
+--------+------------+---------+----------------+----------------------+
|     20 | RESEARCH   | DALLAS  |              5 |                10875 |
|     30 | SALES      | CHICAGO |              6 |                 9400 |
|     40 | OPERATIONS | BOSTON  |              0 |                    0 |
+--------+------------+---------+----------------+----------------------+

(32)、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;