多表查询案例

本文主要是介绍多表查询案例，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

-- 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
);

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

-- 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)
);
-- 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');

-- 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');

-- 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);

-- 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);

-- 1.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
-- 隐式内连接
SELECT
emp.id,
emp.ename,
emp.salary,
job.jname,
job.description
FROM
emp,
job
WHERE
emp.job_id = job.id;

-- 显示内连接
SELECT
emp.id,
emp.ename,
emp.salary,
job.jname,
job.description
FROM
emp
INNER JOIN job ON emp.job_id = job.id;

-- 2.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
emp.id,
emp.ename,
emp.salary,
job.jname,
job.description,
dept.dname,
dept.loc
FROM
emp,
job,
dept
WHERE
emp.job_id = job.id
AND dept.id = emp.dept_id;

-- 3.查询员工姓名，工资，工资等级
SELECT emp.ename,emp.salary,t2.grade FROM emp,salarygrade AS t2 WHERE emp.salary >= t2.losalary AND emp.salary <= t2.hisalary;

-- 4.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 emp.ename,emp.salary,job.jname,job.description,dept.dname,dept.loc,t2.grade from emp,job,dept,salarygrade AS t2 WHERE emp.job_id = job.id AND dept.id = emp.dept_id AND emp.salary >= t2.losalary AND emp.salary <= t2.hisalary;

-- 5.查询出部门编号、部门名称、部门位置、部门人数
SELECT * FROM dept;

SELECT dept.id,dept.dname,dept.loc,t1.COUNT from dept,(SELECT dept_id,COUNT(*) count from emp GROUP BY dept_id) t1 where dept.id = t1.dept_id;

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