1 取得每个部门最高薪水的人员名称
先取得每个部门的最高薪水，然后找出和此薪水和部门编号相同的人。
mysql> select deptno,max(sal) as maxsal from emp group by deptno;
+--------+---------+
| deptno | maxsal |
+--------+---------+
| 20 | 3000.00 |
| 30 | 2850.00 |
| 10 | 5000.00 |
+--------+---------+
mysql> select a.ename,a.deptno,a.sal from emp a join(select deptno,max(sal) as maxsal from emp group by deptno) b on a.sal=b.maxsal and a.deptno=b.deptno;
+-------+--------+---------+
| ename | deptno | sal |
+-------+--------+---------+
| 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平均薪水之上
先求出每个部门的平均薪水
mysql> select deptno,avg(sal) from emp group by deptno;
+--------+-------------+
| deptno | avg(sal) |
+--------+-------------+
| 20 | 2175.000000 |
| 30 | 1566.666667 |
| 10 | 2916.666667 |
+--------+-------------+
然后找出部门中大于其平均薪水的人
mysql> select a.deptno,a.ename,a.sal,b.avgsal from emp a join (select deptno,avg(sal) as avgsal from emp group by deptno) b on a.sal>b.avgsal and a.deptno=b.deptno;
+--------+-------+---------+-------------+
| deptno | ename | sal | avgsal |
+--------+-------+---------+-------------+
| 30 | ALLEN | 1600.00 | 1566.666667 |
| 20 | JONES | 2975.00 | 2175.000000 |
| 30 | BLAKE | 2850.00 | 1566.666667 |
| 20 | SCOTT | 3000.00 | 2175.000000 |
| 10 | KING | 5000.00 | 2916.666667 |
| 20 | FORD | 3000.00 | 2175.000000 |
+--------+-------+---------+-------------+
3 取得部门中所有人的平均的薪水等级
先计算每个人的薪水等级
mysql> select a.deptno,a.ename,a.sal,b.grade from emp a join salgrade b on a.sal between b.losal and b.hisal order by a.deptno;
+--------+--------+---------+-------+
| deptno | ename | sal | grade |
+--------+--------+---------+-------+
| 10 | MILLER | 1300.00 | 2 |
| 10 | CLARK | 2450.00 | 4 |
| 10 | KING | 5000.00 | 5 |
| 20 | SCOTT | 3000.00 | 4 |
| 20 | SIMITH | 800.00 | 1 |
| 20 | ADAMS | 1100.00 | 1 |
| 20 | JONES | 2975.00 | 4 |
| 20 | FORD | 3000.00 | 4 |
| 30 | BLAKE | 2850.00 | 4 |
| 30 | ALLEN | 1600.00 | 3 |
| 30 | TURNER | 1500.00 | 3 |
| 30 | WARD | 1250.00 | 2 |
| 30 | JAMES | 950.00 | 1 |
| 30 | MARTIN | 1250.00 | 2 |
+--------+--------+---------+-------+
然后根据部门分组，由于使用了分组函数，所以只能显示参加分组的字段和分组函数
mysql> select a.deptno,avg(grade) as AvgSalGrade from emp a join salgrade b on a.sal between b.losal and b.hisal group by a.deptno;
+--------+-------------+
| deptno | AvgSalGrade |
+--------+-------------+
| 20 | 2.8000 |
| 30 | 2.5000 |
| 10 | 3.6667 |
+--------+-------------+
4 不准使用组函数Max，给出最高薪水（给出两种解决方案）
方案一，按照薪水降序排列，取第一个
mysql> select ename,sal from emp order by sal desc limit 1;
+-------+---------+
| ename | sal |
+-------+---------+
| KING | 5000.00 |
+-------+---------+
方案二，使用自连接。
mysql> select ename,sal from emp where sal not in
(select a.sal from emp a join emp b on a.sal select deptno, avg(sal) as avgsal from emp group by deptno;
+--------+-------------+
| deptno | avgsal |
+--------+-------------+
| 20 | 2175.000000 |
| 30 | 1566.666667 |
| 10 | 2916.666667 |
+--------+-------------+
再取得最高的平均薪水
mysql> select avg(sal) as avgsal from emp group by deptno order by avgsal desc limit 1;
+-------------+
| avgsal |
+-------------+
| 2916.666667 |
+-------------+
然后取得和最高平均薪水相同的部门（因为可能有多个部门并列最高）
mysql> select deptno,avg(sal) as avgsal from emp group by deptno having avgsal=
-> (select avg(sal) as avgsal from emp group by deptno order by avgsal desc limit 1);
+--------+-------------+
| deptno | avgsal |
+--------+-------------+
| 10 | 2916.666667 |
+--------+-------------+
方案二：与方案一类似，用max取得最高平均薪水
mysql> 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名称
类似上题，将部门表与其连接
mysql> select b.dname,avg(a.sal) as avgsal from emp a join dept b on a.deptno=b.deptno group by b.dname having avgsal=(select max(t.avgsal) from (select avg(sal) as avgsal from emp group by deptno) t);
+------------+-------------+
| dname | avgsal |
+------------+-------------+
| ACCOUNTING | 2916.666667 |
+------------+-------------+
7 求平均薪水的等级最高的部门的部门名称
先求各部门平均薪水的等级
select a.deptno,a.avgsal,b.grade from (select deptno,avg(sal) as avgsal from emp group by deptno) a join salgrade b on avgsal between losal and hisal;
+--------+-------------+-------+
| deptno | avgsal | grade |
+--------+-------------+-------+
| 20 | 2175.000000 | 4 |
| 30 | 1566.666667 | 3 |
| 10 | 2916.666667 | 4 |
+--------+-------------+-------+
取得最高的等级
mysql> select b.grade from (select deptno,avg(sal) as avgsal from emp group by deptno) a join salgrade b on avgsal between losal and hisal order by b.grade desc limit 1;
+-------+
| grade |
+-------+
| 4 |
+-------+
显示平均薪水等级等于最高等级的部门名称
mysql> select d.dname,c.avgsal,c.grade
from
(select a.deptno,a.avgsal,b.grade
from
(select deptno,avg(sal) as avgsal from emp group by deptno) a
join
salgrade b
on
avgsal between losal and hisal) c
join
dept d
on
c.deptno=d.deptno and c.grade=
#最高等级为4
(select b.grade from (select deptno,avg(sal) as avgsal from emp group by deptno) a join salgrade b on avgsal between losal and hisal order by b.grade desc limit 1);
+-------------+-------------+-------+
| dname | avgsal | grade |
+-------------+-------------+-------+
| ACCOUNTING | 2916.666667 | 4 |
| RESEARCHING | 2175.000000 | 4 |
+-------------+-------------+-------+
8 取得比普通员工（员工代码没在mgr字段出现的）最高薪水更高的领导人姓名
先取出普通员工的最高薪水，注意mgr字段里有null，不能直接使用not in 语句
mysql> select max(sal) as cmsal from emp where empno not in (select distinct mgr from emp where mgr is not null);
+---------+
| cmsal |
+---------+
| 1600.00 |
+---------+
取得所有领导人的姓名和薪水
mysql> select ename,sal from emp where empno in (select distinct mgr from emp);
+-------+---------+
| ename | sal |
+-------+---------+
| FORD | 3000.00 |
| BLAKE | 2850.00 |
| KING | 5000.00 |
| JONES | 2975.00 |
| SCOTT | 3000.00 |
| CLARK | 2450.00 |
+-------+---------+
然后取得结果
mysql> select ename,sal from emp where empno in (select distinct mgr from emp) and sal>(select max(sal) as cmsal 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
mysql> select * from emp order by sal desc limit 5;
+-------+-------+-----------+------+------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+-------+-----------+------+------------+---------+------+--------+
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 |
+-------+-------+-----------+------+------------+---------+------+--------+
10 取得薪水最高的第六到第十名员工
mysql> select * from emp order by sal desc limit 5,5;
+-------+--------+----------+------+------------+---------+--------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+--------+----------+------+------------+---------+--------+--------+
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 |
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | NULL | 30 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 |
+-------+--------+----------+------+------------+---------+--------+--------+
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 |
+-------+--------+---------+------+------------+---------+------+--------+
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
+-------+--------+---------+------+------------+---------+------+--------+
12 取得每个薪水等级有多少员工
mysql> select s.grade,count(t.ename) as count from emp t join salgrade s on t.sal between s.losal and s.hisal group by s.grade;
+-------+-------+
| grade | count |
+-------+-------+
| 1 | 3 |
| 3 | 2 |
| 2 | 3 |
| 4 | 5 |
| 5 | 1 |
+-------+-------+
13 面试题
三张表：
学生表S：学号SNO，姓名SNAME
课程表C：课号CNO，课程名CNAME，课程老师CTEACHER
选课表SC：学号SNO，课号CNO，分数SCGRADE
1.显示没选”黎明“老师课的学生
#”黎明“老师的课号
select cno from c where cteacher='黎明';
#没选其课学生的学号
select distinct sno from sc where sno not in (select cno from c where cteacher='黎明');
#没选课学生的姓名
select sname from s where sno in (select distinct sno from sc where sno not in (select cno from c where cteacher='黎明'));
2.列出2门以上（含2门）不及格学生姓名及平均成绩
#2门及以上不及格学生的学号
select sno from sc where scgrade<60 group by sno having count(*)>=2;
#不及格学生姓名
select sname,sno from s where sno in (select sno from sc where scgrade<60 group by sno having count(*)>=2);
#学生的平均成绩
select sno,avg(scgrade) avggrade from sc group by sno;
#联合姓名和平均成绩
select a.sno,a.sname,b.avggrade from (select sname,sno from s where sno in (select sno from sc where scgrade<60 group by sno having count(*)>=2)) a join (select sno,avg(scgrade) avggrade from sc group by sno) b on a.sno=b.sno;
3.学过1号课程和2号课程的所有学生的姓名
#选过1号课程和2号课程的学生学号
select distinct sno from sc where cno=1 or cno=2;
#从s表中取出其姓名
select sno,sname from s where sno in (select distinct sno from sc where cno=1 or cno=2);
最后补充根据视频数据编写的sql文件
create table c(
cno int(2) primary key auto_increment,
cname varchar(32),
cteacher varchar(16)
);
create table s(
sno int(2) primary key auto_increment,
sname varchar(16)
);
create table sc(
sno int(2),
cno int(2),
scgrade int(3),
primary key(sno,cno)
);
insert into c(cname,cteacher)values('语文','张老师');
insert into c(cname,cteacher)values('政治','王老师');
insert into c(cname,cteacher)values('英语','李老师');
insert into c(cname,cteacher)values('数学','赵老师');
insert into c(cname,cteacher)values('物理','黎明');
insert into s(sname)values('学生1');
insert into s(sname)values('学生2');
insert into s(sname)values('学生3');
insert into s(sname)values('学生4');
insert into sc(sno,cno,scgrade)values(1,1,40);
insert into sc(sno,cno,scgrade)values(1,2,30);
insert into sc(sno,cno,scgrade)values(1,3,20);
insert into sc(sno,cno,scgrade)values(1,4,80);
insert into sc(sno,cno,scgrade)values(1,5,60);
insert into sc(sno,cno,scgrade)values(2,1,60);
insert into sc(sno,cno,scgrade)values(2,2,60);
insert into sc(sno,cno,scgrade)values(2,3,60);
insert into sc(sno,cno,scgrade)values(2,4,60);
insert into sc(sno,cno,scgrade)values(2,5,40);
insert into sc(sno,cno,scgrade)values(3,1,60);
insert into sc(sno,cno,scgrade)values(3,2,80);
14 列出所有员工及领导的姓名
最高的领导的领导为null，因此需要使用左连接
mysql> select a.ename as empname,b.ename as leadname from emp a left join emp b on a.mgr=b.empno;
+---------+----------+
| empname | leadname |
+---------+----------+
| SIMITH | 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上级的所有员工的编号、姓名、部门名称
mysql> select e.empno,e.ename,e.hiredate,l.ename,l.hiredate from emp e join emp l on e.mgr=l.empno and e.hiredate select d.dname,e.* from dept d left join emp e on d.deptno=e.deptno;
+-------------+-------+--------+-----------+------+------------+---------+---------+--------+
| dname | empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------------+-------+--------+-----------+------+------------+---------+---------+--------+
| RESEARCHING | 7369 | SIMITH | CLERK | 7902 | 1980-12-17 | 800.00 | NULL | 20 |
| SALES | 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 |
| RESEARCHING | 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 |
| 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 |
| ACCOUNTING | 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 |
| RESEARCHING | 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| ACCOUNTING | 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 |
| SALES | 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | NULL | 30 |
| RESEARCHING | 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 |
| SALES | 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 |
| RESEARCHING | 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
| ACCOUNTING | 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
| OPERATIONS | NULL | NULL | NULL | NULL | NULL | NULL | NULL | NULL |
+-------------+-------+--------+-----------+------+------------+---------+---------+--------+
17 列出至少有5名员工的所有部门
mysql> select d.dname,count(e.empno) as number from dept d join emp e on d.deptno=e.deptno group by d.deptno having number>=5;
+-------------+--------+
| dname | number |
+-------------+--------+
| RESEARCHING | 5 |
| SALES | 6 |
+-------------+--------+
18 列出薪水比simith多的所有员工信息
mysql> select * from emp where sal>(select sal from emp where ename='simith');
+-------+--------+-----------+------+------------+---------+---------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+--------+-----------+------+------------+---------+---------+--------+
| 7499 | ALLEN | SALESMAN | 7698 | 1981-02-20 | 1600.00 | 300.00 | 30 |
| 7521 | WARD | SALESMAN | 7698 | 1981-02-22 | 1250.00 | 500.00 | 30 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 |
| 7654 | MARTIN | SALESMAN | 7698 | 1981-09-28 | 1250.00 | 1400.00 | 30 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 |
| 7844 | TURNER | SALESMAN | 7698 | 1981-09-08 | 1500.00 | NULL | 30 |
| 7876 | ADAMS | CLERK | 7788 | 1987-05-23 | 1100.00 | NULL | 20 |
| 7900 | JAMES | CLERK | 7698 | 1981-12-03 | 950.00 | NULL | 30 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 |
| 7934 | MILLER | CLERK | 7782 | 1982-01-23 | 1300.00 | NULL | 10 |
+-------+--------+-----------+------+------------+---------+---------+--------+
19 列出所有岗位为clerk的姓名及部门名称，部门人数
先取出每个部门的人数
mysql> select d.deptno,d.dname,count(e.empno) as numbers from dept d join emp e on d.deptno=e.deptno group by e.deptno;
+--------+-------------+---------+
| deptno | dname | numbers |
+--------+-------------+---------+
| 20 | RESEARCHING | 5 |
| 30 | SALES | 6 |
| 10 | ACCOUNTING | 3 |
+--------+-------------+---------+
然后将上表作为临时表与emp表连接
mysql> select a.ename,t.dname,t.numbers from emp a join (select d.deptno,d.dname,count(e.empno) as numbers from dept d join emp e on d.deptno=e.deptno group by e.deptno) t on a.deptno=t.deptno and a.job='clerk';
+--------+-------------+---------+
| ename | dname | numbers |
+--------+-------------+---------+
| SIMITH | RESEARCHING | 5 |
| ADAMS | RESEARCHING | 5 |
| JAMES | SALES | 6 |
| MILLER | ACCOUNTING | 3 |
+--------+-------------+---------+
20 列出最低薪水大于1500的各种工作及从事此工作的全部雇员人数
先取出最低薪水大于1500的工作
mysql> select job,min(sal) as minsal from emp group by job having minsal>1500;
+-----------+---------+
| job | minsal |
+-----------+---------+
| MANAGER | 2450.00 |
| ANALYST | 3000.00 |
| PRESIDENT | 5000.00 |
+-----------+---------+
找出工作为这些职业的职员
mysql> select a.*,b.minsal from emp a join (select job,min(sal) as minsal from emp group by job having minsal>1500) b where a.job=b.job;
+-------+-------+-----------+------+------------+---------+------+--------+---------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | minsal |
+-------+-------+-----------+------+------------+---------+------+--------+---------+
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 | 2975.00 | NULL | 20 | 2450.00 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 | 2850.00 | NULL | 30 | 2450.00 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 | 2450.00 | NULL | 10 | 2450.00 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 | 3000.00 | NULL | 20 | 3000.00 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 | 5000.00 | NULL | 10 | 5000.00 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 | 3000.00 | NULL | 20 | 3000.00 |
+-------+-------+-----------+------+------------+---------+------+--------+---------+
最后计数
mysql> select t.job,count(t.empno),t.minsal from (select a.*,b.minsal from emp a join (select job,min(sal) as minsal from emp group by job having minsal>1500) b where a.job=b.job) t group by job;
+-----------+----------------+---------+
| job | count(t.empno) | minsal |
+-----------+----------------+---------+
| MANAGER | 3 | 2450.00 |
| ANALYST | 2 | 3000.00 |
| PRESIDENT | 1 | 5000.00 |
+-----------+----------------+---------+
21 列出在部门sales工作的员工的姓名，假定不知道销售部的部门编号
mysql> select e.ename,d.dname from emp e join dept d on e.deptno=d.deptno and d.dname='sales';
+--------+-------+
| ename | dname |
+--------+-------+
| ALLEN | SALES |
| WARD | SALES |
| MARTIN | SALES |
| BLAKE | SALES |
| TURNER | SALES |
| JAMES | SALES |
+--------+-------+
22 列出薪水高于公司平均薪水的所有员工，所在部门，上级领导，薪水等级
需要使用多表连接，将三张表连接在一起。
先取出公司平均薪水
mysql> select avg(sal) as avgsal from emp;
+-------------+
| avgsal |
+-------------+
| 2073.214286 |
+-------------+
然后多表连接
mysql> select e.ename,e.sal,d.dname,s.grade
from
emp e
join
dept d
on
e.deptno=d.deptno
join
salgrade s
on
e.sal between s.losal and s.hisal
having
sal>(select avg(sal) as avgsal from emp);
+-------+---------+-------------+-------+
| ename | sal | dname | grade |
+-------+---------+-------------+-------+
| JONES | 2975.00 | RESEARCHING | 4 |
| BLAKE | 2850.00 | SALES | 4 |
| CLARK | 2450.00 | ACCOUNTING | 4 |
| SCOTT | 3000.00 | RESEARCHING | 4 |
| KING | 5000.00 | ACCOUNTING | 5 |
| FORD | 3000.00 | RESEARCHING | 4 |
+-------+---------+-------------+-------+
23 列出与scott从事相同工作的所有员工及部门名称
先找出scott的岗位
mysql> select job from emp where ename='scott';
+---------+
| job |
+---------+
| ANALYST |
+---------+
然后找出从事此工作的员工并与部门表连接显示部门名，注意排除scott本人
mysql> select e.ename,d.dname from emp e join dept d where e.deptno=d.deptno and e.job=(select job from emp where ename='scott') and e.ename<>'scott';
+-------+-------------+
| ename | dname |
+-------+-------------+
| FORD | RESEARCHING |
+-------+-------------+
24 列出薪水等于部门30中员工的薪水的其他员工的姓名和薪水
取出部门30的各个员工的薪水
mysql> select sal from emp where deptno=30;
+---------+
| sal |
+---------+
| 1600.00 |
| 1250.00 |
| 1250.00 |
| 2850.00 |
| 1500.00 |
| 950.00 |
+---------+
然后找出其他部门中是否有员工工资与上表中数据相同
mysql> select ename,sal from emp where sal in (select sal from emp where deptno=30) and deptno<>30;
Empty set (0.00 sec)
结果为空
25 列出薪水高于部门30的全部员工的员工姓名，薪水，部门名称
先取出部门30的最高薪水
mysql> select sal from emp where deptno=30 order by sal desc limit 1;
+---------+
| sal |
+---------+
| 2850.00 |
+---------+
然后连接员工表和部门表
mysql> select e.ename,e.sal,d.dname from emp e join dept d where e.deptno=d.deptno and e.sal>(select sal from emp where deptno=30 order by sal desc limit 1);
+-------+---------+-------------+
| ename | sal | dname |
+-------+---------+-------------+
| JONES | 2975.00 | RESEARCHING |
| SCOTT | 3000.00 | RESEARCHING |
| KING | 5000.00 | ACCOUNTING |
| FORD | 3000.00 | RESEARCHING |
+-------+---------+-------------+
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
先取出每个部门的员工数量
mysql> select d.deptno,count(e.ename)as number from dept d left join emp e on d.deptno=e.deptno group by d.deptno;
+--------+--------+
| deptno | number |
+--------+--------+
| 20 | 5 |
| 30 | 6 |
| 10 | 3 |
| 40 | 0 |
+--------+--------+
平均薪水
mysql> select d.deptno,count(e.ename)as number,ifnull(avg(e.sal),0) as avgsal from dept d left join emp e on d.deptno=e.deptno group by d.deptno;
+--------+--------+-------------+
| deptno | number | avgsal |
+--------+--------+-------------+
| 20 | 5 | 2175.000000 |
| 30 | 6 | 1566.666667 |
| 10 | 3 | 2916.666667 |
| 40 | 0 | 0.000000 |
+--------+--------+-------------+
使用to_days()将时间转换为公元元年到某时间点的天数
mysql> select d.deptno,
count(e.ename)as number,ifnull(avg(e.sal),0) as avgsal,
ifnull(avg((to_days(now())-to_days(e.hiredate))/365),0) as avgtime
from
dept d
left join
emp e
on
d.deptno=e.deptno
group by
d.deptno;
+--------+--------+-------------+-------------+
| deptno | number | avgsal | avgtime |
+--------+--------+-------------+-------------+
| 20 | 5 | 2175.000000 | 35.57588000 |
| 30 | 6 | 1566.666667 | 37.84750000 |
| 10 | 3 | 2916.666667 | 37.54886667 |
| 40 | 0 | 0.000000 | 0.00000000 |
+--------+--------+-------------+-------------+
27 列出所有员工的姓名、部门名称、工资
mysql> select e.ename,d.dname,e.sal from emp e join dept d on d.deptno=e.deptno;
+--------+-------------+---------+
| ename | dname | sal |
+--------+-------------+---------+
| SIMITH | RESEARCHING | 800.00 |
| ALLEN | SALES | 1600.00 |
| WARD | SALES | 1250.00 |
| JONES | RESEARCHING | 2975.00 |
| MARTIN | SALES | 1250.00 |
| BLAKE | SALES | 2850.00 |
| CLARK | ACCOUNTING | 2450.00 |
| SCOTT | RESEARCHING | 3000.00 |
| KING | ACCOUNTING | 5000.00 |
| TURNER | SALES | 1500.00 |
| ADAMS | RESEARCHING | 1100.00 |
| JAMES | SALES | 950.00 |
| FORD | RESEARCHING | 3000.00 |
| MILLER | ACCOUNTING | 1300.00 |
+--------+-------------+---------+
28 列出所有部门的详细信息和人数
mysql> select d.*,count(e.ename) as totalemp from dept d left join emp e on d.deptno=e.deptno group by d.deptno;
+--------+-------------+----------+----------+
| deptno | dname | loc | totalemp |
+--------+-------------+----------+----------+
| 20 | RESEARCHING | DALLAS | 5 |
| 30 | SALES | CHICAGO | 6 |
| 10 | ACCOUNTING | NEW YORK | 3 |
| 40 | OPERATIONS | BOSTON | 0 |
+--------+-------------+----------+----------+
29 列出各种工作的最低工资以及从事此工作的雇员姓名
先取出各种工作的最低工资
mysql> select job,min(sal) as minsal from emp group by job;
+-----------+---------+
| job | minsal |
+-----------+---------+
| CLERK | 800.00 |
| SALESMAN | 1250.00 |
| MANAGER | 2450.00 |
| ANALYST | 3000.00 |
| PRESIDENT | 5000.00 |
+-----------+---------+
然后从员工表emp中找出岗位和工资与上表相同的员工
mysql> select e.ename,t.job,t.minsal from emp e join (select job,min(sal) as minsal from emp group by job) t on e.sal=t.minsal and e.job=t.job;
+--------+-----------+---------+
| ename | job | minsal |
+--------+-----------+---------+
| SIMITH | 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的最低薪水
mysql> select min(sal),deptno from emp where job='manager' group by deptno;
+----------+--------+
| min(sal) | deptno |
+----------+--------+
| 2975.00 | 20 |
| 2850.00 | 30 |
| 2450.00 | 10 |
+----------+--------+
显示姓名和职业的话，可以再与员工表emp进行表连接
mysql> select e.ename,e.job,t.minsal,t.deptno from emp e join (select min(sal) minsal,deptno from emp where job='manager' group by deptno) t on e.sal=t.minsal and e.deptno=t.deptno;
+-------+---------+---------+--------+
| ename | job | minsal | deptno |
+-------+---------+---------+--------+
| JONES | MANAGER | 2975.00 | 20 |
| BLAKE | MANAGER | 2850.00 | 30 |
| CLARK | MANAGER | 2450.00 | 10 |
+-------+---------+---------+--------+
31 列出员工的年工资，按年薪从低到高排序
mysql> select ename,sal*12 as yearsal from emp order by sal desc;
+--------+----------+
| ename | yearsal |
+--------+----------+
| KING | 60000.00 |
| SCOTT | 36000.00 |
| FORD | 36000.00 |
| JONES | 35700.00 |
| BLAKE | 34200.00 |
| CLARK | 29400.00 |
| ALLEN | 19200.00 |
| TURNER | 18000.00 |
| MILLER | 15600.00 |
| WARD | 15000.00 |
| MARTIN | 15000.00 |
| ADAMS | 13200.00 |
| JAMES | 11400.00 |
| SIMITH | 9600.00 |
+--------+----------+
32 求出员工领导的薪水超过3000的员工姓名和领导姓名
mysql> select a.ename empname,b.ename leadname,b.sal from emp a join emp b on a.mgr=b.empno and b.sal>3000;
+---------+----------+---------+
| empname | leadname | sal |
+---------+----------+---------+
| JONES | KING | 5000.00 |
| BLAKE | KING | 5000.00 |
| CLARK | KING | 5000.00 |
+---------+----------+---------+
33 求出部门名称中，带有‘s’字符的部门员工的工资合计，部门人数
mysql> select d.deptno,d.dname,ifnull(sum(e.sal),0) as sumsal,ifnull(count(e.ename),0) as totalemp from dept d left join emp e on d.deptno=e.deptno where d.dname like '%s%' group by d.deptno;
+--------+-------------+----------+----------+
| deptno | dname | sumsal | totalemp |
+--------+-------------+----------+----------+
| 20 | RESEARCHING | 10875.00 | 5 |
| 30 | SALES | 9400.00 | 6 |
| 40 | OPERATIONS | 0.00 | 0 |
+--------+-------------+----------+----------+
34 给任职时间超过30年的员工加薪10%
update emp set sal=sal*1.1 where (to_days(now())-to_days(hiredate))/365>30;
