数据库表
CREATE TABLE departments (
dept_no CHAR(4) PRIMARY KEY COMMENT '部门编码',
dept_name VARCHAR(40) NOT NULL UNIQUE COMMENT '部门名称'
) COMMENT '部门表';
CREATE TABLE dept_emp (
emp_no INT NOT NULL COMMENT '部门编码',
dept_no CHAR(4) NOT NULL COMMENT '雇员ID',
FOREIGN KEY (emp_no) REFERENCES employees (emp_no) ON DELETE CASCADE,
FOREIGN KEY (dept_no) REFERENCES departments (dept_no) ON DELETE CASCADE,
PRIMARY KEY (emp_no,dept_no)
) COMMENT '雇员与部门关系表';
CREATE TABLE salaries (
emp_no INT NOT NULL COMMENT '雇员ID',
salary INT NOT NULL COMMENT '工资',
month INT NOT NULL COMMENT '月份',
level INT NOT NULL COMMENT '工资等级',
FOREIGN KEY (emp_no) REFERENCES employees (emp_no) ON DELETE CASCADE
) COMMENT '薪资表';
-- 向雇员表中插入数据
insert into employees values
('100','1990-08-19','JACK','M','20160811'),
('101','1970-08-12','TOM','M','20100606'),
('102','1996-03-19','JAMES','M','20140101'),
('103','1987-04-28','KETTY','F','20130910'),
('104','1983-05-19','JIM','F','20160418');
-- 向部门表中插入数据
insert into departments values
('1001','A'),
('1002','B'),
('1003','C'),
('1004','D');
-- 向部门与雇员关系表中插入数据
insert into dept_emp values
('100','1001'),
('101','1001'),
('102','1002'),
('103','1003'),
('104','1004');
-- 想工资表中插入数据
insert into salaries values
('100','12000','201601',2),
('101','9000','201601',1),
('102','90000','201601',10),
('103','2300','201601',1),
('104','4000','201601',1),
('100','12000','201602',2),
('101','9000','201602',1),
('102','90000','201602',10),
('103','2300','201602',1),
('104','4000','201602',1),
('100','12000','201603',2),
('101','9000','201603',1),
('102','90000','201603',10),
('103','2300','201603',1),
('104','4000','201603',1),
('100','12000','201604',2),
('101','9000','201604',1),
('102','90000','201604',10),
('103','2300','201604',1),
('104','4000','201604',1);
1.查看部门表中的所有记录
select * from departments
2.查看员工表中的所有记录
select * from employees
3.查询所有员工所属的部门
select a.emp_no,a.name,b.dept_no,b.dept_name from employees a
left join dept_emp b on a.emp_no = b.emp_no
left join departments c on c.dept_no = a.dept_no
4.查询属于A部门的员工
select a.name from employees a
left join dept_emp b on a.emp_no = b.emp_no
left join departments c on c.dept_no = b.dept_no where c.dept_name = 'A'
5.查询属于A部门员工的每月平均工资
SELECT AVG(salary),d.month FROM employees a
LEFT JOIN dept_emp b ON a.emp_no = b.emp_no
LEFT JOIN departments c ON c.dept_no = b.dept_no
LEFT JOIN salaries d ON a.emp_no = d.emp_no WHERE c.dept_name = 'A' group by d.month
6.查询所有员工的薪水总和
select sum(salary) from salaries
7.查询各个部门的员工平均工资
select avg(a.salary),b.dept_no from salaries a join dept_emp b on a.emp_no = b.emp_no group by b.dept_no
8.查询不同工资水平下各有多少员工
SELECT COUNT(DISTINCT emp_no),LEVEL FROM salaries GROUP BY LEVEL
9.查询名字中包含M的员工的每月平均工资
SELECT AVG(salary),MONTH FROM salaries a
LEFT JOIN employees b ON a.emp_no = b.emp_no WHERE b.name LIKE '%M%' GROUP BY MONTH
10.查询所有女性中工资最高的员工
select distinct b.name,b.emp_no from salaries a
left join employees b on a.emp_no = b.emp_no where salary = ( select max(salary) from salaries a left join employees b on a.emp_no = b.emp_no where b.gender = 'F') and b.gender = 'F'
11.查询每月员工工资之和大于30000的部门有哪些
SELECT SUM(a.salary),b.dept_no,a.month,c.dept_name FROM salaries a
JOIN dept_emp b ON a.emp_no = b.emp_no
LEFT JOIN departments c ON c.dept_no = b.dept_no GROUP BY b.dept_no,a.month
HAVING SUM(a.salary) > 30000
