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
);

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‘);

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‘);

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);

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);

SELECT 
    e.id,e.`ename`,e.`salary`,j.`jname`,j.`description` 
FROM 
    emp e,job j 
WHERE 
    e.job_id= j.id

-- select * from emp,job,dept;
SELECT 
    e.`id`,e.`ename`,e.`salary`,j.`jname`,j.`description`,d.dname,d.loc
FROM 
    emp e,job j,dept d 
WHERE 
    e.`job_id` = j.`id`
AND
    e.`dept_id` = d.id

SELECT 
    e.ename,e.salary,s.grade 
FROM
    emp e,salarygrade s 
WHERE 
    e.`salary` BETWEEN s.losalary AND hisalary;

SELECT 
    e.`ename`,e.`salary`,j.`jname`,j.`description`,d.`dname`,d.`loc`,s.`grade`
FROM
    emp e,dept d,salarygrade s,job j
WHERE
    e.`dept_id` = d.`id` 
AND
    e.`salary` BETWEEN s.`losalary` AND s.`hisalary`
AND 
    e.`job_id` = j.`id`

SELECT 
    d.`id`,d.`dname`,d.`loc`,e.nums
FROM
    dept d,(SELECT dept_id, COUNT(*) nums FROM emp GROUP BY dept_id) e
WHERE
    d.`id` = e.`dept_id`

-- SELECT id,ename,mgr FROM emp;

SELECT
    e.`ename`,t.ename
FROM
    emp e
LEFT JOIN  
    (SELECT id,ename FROM emp) t
ON
    e.`mgr` = t.id