首先需要创建数据库，并传值：

-- 部门表
CREATE TABLE dept (
  id INT PRIMARY KEY PRIMARY KEY, -- 部门id
  dname VARCHAR(50), -- 部门名称
  loc VARCHAR(50) -- 部门所在地
);

-- 添加4个部门
INSERT INTO dept(id,dname,loc) VALUES 
(10,'教研部','北京'),
(20,'学工部','上海'),
(30,'销售部','广州'),
(40,'财务部','深圳');



-- 职务表，职务名称，职务描述
CREATE TABLE job (
  id INT PRIMARY KEY,
  jname VARCHAR(20),
  description VARCHAR(50)
);

-- 添加4个职务
INSERT INTO job (id, jname, description) VALUES
(1, '董事长', '管理整个公司，接单'),
(2, '经理', '管理部门员工'),
(3, '销售员', '向客人推销产品'),
(4, '文员', '使用办公软件');


-- 员工表
CREATE TABLE emp (
  id INT PRIMARY KEY, -- 员工id
  ename VARCHAR(50), -- 员工姓名
  job_id INT, -- 职务id
  mgr INT , -- 上级领导
  joindate DATE, -- 入职日期
  salary DECIMAL(7,2), -- 工资
  bonus DECIMAL(7,2), -- 奖金
  dept_id INT, -- 所在部门编号
  CONSTRAINT emp_jobid_ref_job_id_fk FOREIGN KEY (job_id) REFERENCES job (id),
  CONSTRAINT emp_deptid_ref_dept_id_fk FOREIGN KEY (dept_id) REFERENCES dept (id)
);

-- 添加员工
INSERT INTO emp(id,ename,job_id,mgr,joindate,salary,bonus,dept_id) VALUES 
(1001,'孙悟空',4,1004,'2000-12-17','8000.00',NULL,20),
(1002,'卢俊义',3,1006,'2001-02-20','16000.00','3000.00',30),
(1003,'林冲',3,1006,'2001-02-22','12500.00','5000.00',30),
(1004,'唐僧',2,1009,'2001-04-02','29750.00',NULL,20),
(1005,'李逵',4,1006,'2001-09-28','12500.00','14000.00',30),
(1006,'宋江',2,1009,'2001-05-01','28500.00',NULL,30),
(1007,'刘备',2,1009,'2001-09-01','24500.00',NULL,10),
(1008,'猪八戒',4,1004,'2007-04-19','30000.00',NULL,20),
(1009,'罗贯中',1,NULL,'2001-11-17','50000.00',NULL,10),
(1010,'吴用',3,1006,'2001-09-08','15000.00','0.00',30),
(1011,'沙僧',4,1004,'2007-05-23','11000.00',NULL,20),
(1012,'李逵',4,1006,'2001-12-03','9500.00',NULL,30),
(1013,'小白龙',4,1004,'2001-12-03','30000.00',NULL,20),
(1014,'关羽',4,1007,'2002-01-23','13000.00',NULL,10);


-- 工资等级表
CREATE TABLE salarygrade (
  grade INT PRIMARY KEY,   -- 级别
  losalary INT,  -- 最低工资
  hisalary INT -- 最高工资
);

-- 添加5个工资等级
INSERT INTO salarygrade(grade,losalary,hisalary) VALUES 
(1,7000,12000),
(2,12010,14000),
(3,14010,20000),
(4,20010,30000),
(5,30010,99990);

然后就可以对数据进行查询，下面每个代码块都有题目：

-- 查询所有员工信息。查询员工编号，员工姓名，工资，职务名称，职务描述
SELECT 
	e.`id`,e.ename,e.salary,j.`jname`,j.`description` 
FROM
	job j JOIN emp e
ON 
	j.`id`=e.`job_id`
--  查询员工编号，员工姓名，工资，职务名称，职务描述，部门名称，部门位置
SELECT 
	e.`id`,e.`ename`,e.`salary`,j.`jname`,j.`description`,d.dname,d.loc
FROM
	job j JOIN emp e JOIN dept d
ON 
	j.`id`=e.`job_id` AND d.id=e.`dept_id`
-- 查询员工姓名，工资，工资等级
SELECT 
	e.`ename`,e.`salary`,s.grade
FROM
	emp e JOIN salarygrade s
ON 
	e.`salary` BETWEEN s.losalary AND hisalary
-- 查询员工姓名，工资，职务名称，职务描述，部门名称，部门位置，工资等级
SELECT 
	e.`ename`,e.`salary`,j.`jname`,j.`description`,d.dname,d.loc,s.grade
FROM
	emp e JOIN job j JOIN dept d JOIN salarygrade s
ON 
	j.`id`=e.`job_id` AND e.`dept_id`=d.id AND e.`salary` BETWEEN s.losalary AND hisalary
-- 查询出部门编号、部门名称、部门位置、部门人数
SELECT 
	d.*,e.total
FROM
	dept d JOIN (SELECT  COUNT(*) total,dept_id FROM emp GROUP BY dept_id) e
ON 
	e.`dept_id`=d.id
-- 查询所有员工的姓名及其直接上级的姓名,没有领导的员工也需要查询
SELECT
	e.`ename`,em.ename
FROM 
	emp e JOIN emp em
ON 
	e.`id`=em.mgr