--1，取得每个部门中的最高薪水的人员名称。
第一步：取得每个部门的最高薪水。
第二步：把上面获得的结果作为临时表t，然后与emp表进行内连接中的等值连接，连接条件为emp表的deptno,sal和t中的deptno,maxsal相等。
SELECT d.deptno,d.dname,max(e.sal)
from dept d INNER JOIN emp e on d.deptno=e.deptno GROUP BY d.deptno
SELECT s.dname,e1.ename
FROM emp e1 INNER JOIN(SELECT d.deptno,d.dname,max(e.sal) maxsal
from dept d INNER JOIN emp e on d.deptno=e.deptno GROUP BY d.deptno ) s on e1.deptno=s.deptno and e1.sal=s.maxsal
--2，哪些人的薪水在部门的平均薪水之上。
select d.deptno ,d.dname,avg(e.sal) avgsal
from dept d INNER JOIN emp e on d.deptno=e.deptno GROUP BY d.deptno
select e1.ename
from emp e1 INNER JOIN (select d.deptno ,d.dname,avg(e.sal) avgsal
from dept d INNER JOIN emp e on d.deptno=e.deptno GROUP BY d.deptno) s on e1.deptno=s.deptno
and e1.sal>s.avgsal
--3
--3.1取得部门（所有人的）平均薪水的等级。
select avg(e.sal) avgsal
from dept d INNER JOIN emp e on d.deptno=e.deptno
select sal.grade
from salgrade sal INNER JOIN (select avg(e.sal) avgsal
from dept d INNER JOIN emp e on d.deptno=e.deptno ) s on s.avgsal BETWEEN
sal.losal and sal.hisal
--3.2取得每个部门中所有人的薪水等级的平均等级。
select d.dname,avg( s.grade) avg
from dept d INNER JOIN emp e on d.deptno=e.deptno INNER JOIN salgrade s on e.sal BETWEEN
s.losal and s.hisal GROUP BY d.deptno
select avg(s.grade)
from salgrade s INNER JOIN (select s.grade
from dept d INNER JOIN emp e on d.deptno=e.deptno INNER JOIN salgrade s on e.sal BETWEEN
s.losal and s.hisal ) s1 on s.grade=s1.grade
select s.dname, sal.grade
from salgrade sal INNER JOIN (
select avg(e.sal) avgsal ,d.dname dname
from dept d INNER JOIN emp e on d.deptno=e.deptno GROUP BY d.deptno ) s on s.avgsal BETWEEN
sal.losal and sal.hisal
--4，不准用分组函数（Max），取得最高薪水。
select e.sal 最高薪水
FROM emp e where e.sal>=all(select sal from emp where sal!=e.sal )
SELECT sal
FROM emp ORDER BY sal desc LIMIT 1
--5、取得平均薪水最高的部门的部门编号
select d.dname,avg(e.sal) avg
from emp e INNER JOIN dept d on e.deptno=d.deptno GROUP BY d.deptno
select deptno
from (select deptno, avg(sal) as avg_sal from emp GROUP by deptno) s
order by avg_sal desc
limit 1;
--6、取得平均薪水最高的部门的部门名称。
select s.dname
from (select e.deptno deptno, d.dname dname,avg(e.sal) avg
from emp e left JOIN dept d on e.deptno=d.deptno GROUP BY e.deptno) s ORDER BY avg desc LIMIT 1
--7、求平均薪水的等级最低的部门的部门名称。
select d.dname,avg( s.grade) avg
from dept d INNER JOIN emp e on d.deptno=e.deptno INNER JOIN salgrade s on e.sal BETWEEN
s.losal and s.hisal GROUP BY d.deptno
select s.dname
from ( select d.dname,avg( s.grade) avg
from dept d INNER JOIN emp e on d.deptno=e.deptno INNER JOIN salgrade s on e.sal BETWEEN
s.losal and s.hisal GROUP BY d.deptno) s ORDER BY avg LIMIT 1
附表
CREATE TABLE student (
id INT(10) PRIMARY KEY auto_increment , --学生ID 自增
name VARCHAR(20) NOT NULL , -- 学生姓名
sex VARCHAR(4) , -- 学生性别
birth YEAR, -- 学生出生年份
department VARCHAR(20) , --所在院系
address VARCHAR(50) -- 家庭住址
);
CREATE TABLE score (
id INT(10) NOT NULL PRIMARY KEY AUTO_INCREMENT , --自增ID
stu_id INT(10) NOT NULL , --学生ID ，外键创建可
有可无
c_name VARCHAR(20) , -- 学科名称
grade INT(10) -- 分数
);
INSERT INTO student VALUES( 901,'张老大', '男',1985,'计算机系', '北京市海淀区');
INSERT INTO student VALUES( 902,'张老二', '男',1986,'中文系', '北京市昌平区');
INSERT INTO student VALUES( 903,'张三', '女',1990,'中文系', '湖南省永州市');
INSERT INTO student VALUES( 904,'李四', '男',1990,'英语系', '辽宁省阜新市');
INSERT INTO student VALUES( 905,'王五', '女',1991,'英语系', '福建省厦门市');
INSERT INTO student VALUES( 906,'王六', '男',1988,'计算机系', '湖南省衡阳市');
INSERT INTO score VALUES(NULL,901, '计算机',98);
INSERT INTO score VALUES(NULL,901, '英语', 80);
INSERT INTO score VALUES(NULL,902, '计算机',65);
INSERT INTO score VALUES(NULL,902, '中文',88);
INSERT INTO score VALUES(NULL,903, '中文',95);
INSERT INTO score VALUES(NULL,904, '计算机',70);
INSERT INTO score VALUES(NULL,904, '英语',92);
INSERT INTO score VALUES(NULL,905, '英语',94);
INSERT INTO score VALUES(NULL,906, '计算机',90);
INSERT INTO score VALUES(NULL,906, '英语',85);
CREATE TABLE `emp` (
`empno` int(11) NOT NULL AUTO_INCREMENT,
`ename` varchar(50) DEFAULT NULL,
`job` varchar(50) DEFAULT NULL,
`mgr` int(11) DEFAULT NULL,
`hiredate` date DEFAULT NULL,
`sal` decimal(7,2) DEFAULT NULL,
`comm` decimal(7,2) DEFAULT NULL,
`deptno` int(11) DEFAULT NULL,
PRIMARY KEY (`empno`)
)
INSERT INTO `emp` VALUES ('1001', '张贝贝', '文员', '1013', '2000-12-17', '8000.00', null, '20');
INSERT INTO `emp` VALUES ('1002', '黛依思', '销售员', '1006', '2001-02-20', '16000.00', '3000.00', '30');
INSERT INTO `emp` VALUES ('1003', '李莫愁', '销售员', '1006', '2001-02-22', '12500.00', '5000.00', '30');
INSERT INTO `emp` VALUES ('1004', '刘备', '经理', '1009', '2001-01-02', '29750.00', null, '20');
INSERT INTO `emp` VALUES ('1005', '谢逊', '销售员', '1006', '2001-09-28', '12500.00', '14000.00', '30');
INSERT INTO `emp` VALUES ('1006', '关羽', '经理', '1009', '2001-05-01', '27000.00', null, '30');
INSERT INTO `emp` VALUES ('1007', '张飞', '经理', '1009', '2003-04-01', '25000.00', null, '10');
INSERT INTO `emp` VALUES ('1008', '诸葛亮', '分析师', '1004', '2007-04-09', '30000.00', null, '20');
INSERT INTO `emp` VALUES ('1009', '黄盖', '文员', '1007', '2005-01-01', '9500.00', '1000.00', '10');
INSERT INTO `emp` VALUES ('1010', '张三', '董事长', null, '1998-01-01', '50000.00', null, '10');
INSERT INTO `emp` VALUES ('1011', '李四', '保洁', '1001', '2023-10-01', '80000.00', '10000.00', '50');
CREATE TABLE dept(
deptno INT PRIMARY KEY,
dname varchar(14),
loc varchar(13)
);
INSERT INTO `dept` VALUES ('10', '教研部', '北京');
INSERT INTO `dept` VALUES ('20', '学工部', '郑州');
INSERT INTO `dept` VALUES ('30', '销售部', '广州');
INSERT INTO `dept` VALUES ('40', '财务部', '深圳');
CREATE TABLE `salgrade` (
`grade` int(11) NOT NULL DEFAULT '0',
`losal` decimal(7,2) DEFAULT NULL,
`hisal` decimal(7,2) DEFAULT NULL
)
INSERT INTO `salgrade` VALUES ('1', '7000.00', '12000.00');
INSERT INTO `salgrade` VALUES ('2', '12010.00', '14000.00');
INSERT INTO `salgrade` VALUES ('3', '14010.00', '20000.00');
INSERT INTO `salgrade` VALUES ('4', '20010.00', '30000.00');
INSERT INTO `salgrade` VALUES ('5', '30010.00', '99999.00');