MySQL多表操作练习题

数据准备

CREATE table dept(
deptno INT PRIMARY KEY,
dname VARCHAR(14),
loc VARCHAR(13)
);

INSERT INTO dept VALUES(10,'accounting','new york');
INSERT INTO dept VALUES(20, 'research', 'dallas');
INSERT INTO dept VALUES(30, 'sales', 'chicago');
INSERT INTO dept VALUES(40, 'operations', 'boston');

-- 创建员工表
CREATE TABLE emp(
empno	INT PRIMARY KEY,
ename VARCHAR(10),
job VARCHAR(9),
mgr INT,
hiredate date,
sal DOUBLE,
comm DOUBLE,
deptno INT
);

-- 添加 部门和员工之间的主外键关系
ALTER TABLE emp ADD CONSTRAINT FOREIGN KEY emp(deptno) REFERENCES dept (deptno);

INSERT INTO emp VALUES(7369,'smith','clerk',7902,'1980-12-17',800,null,20);
INSERT INTO emp VALUES(7499, 'allen', 'salesman', 7698, '1981-02-20', 1600, 300, 30);
INSERT INTO emp VALUES(7521, 'ward', 'salesman', 7698, '1921-02-22', 1250, 500, 30);
INSERT INTO emp VALUES(7566, 'jones', 'manager', 7839, '1981-04-02', 2975, NULL, 20);
INSERT INTO emp VALUES(7654, 'martin', 'salesman', 7698, '1981-09-28', 1250, 1400, 30);
INSERT INTO emp VALUES(7698, 'blacke', 'manager', 7839, '1981-05-01', 2850, NULL, 30);
INSERT INTO emp VALUES (7782, 'clark', 'manager', 7839, '1981-06-09', 2450, NULL, 10);
INSERT INTO emp VALUES(7788, 'scott', 'analyst', 7566, '1987-07-03', 3000, NULL, 20);
INSERT INTO emp VALUES(7839, 'king', 'president', NULL, '1981-11-17', 5000, NULL, 10);
INSERT INTO emp VALUES(7844, 'turner', 'salesman', 7698, '1981-09-08', 1500, 0, 30);
INSERT INTO emp VALUES(7876, 'adams', 'clerk', 7788, '1987-07-13', 1100, NULL, 20);
INSERT INTO emp VALUES(7900, 'james', 'clerk', 7698, '1981-12-03', 95, NULL, 30);
INSERT INTO emp VALUES(7902, 'ford', 'analyst', 7566, '1981-12-03', 3000, NULL, 20);
INSERT INTO emp VALUES(7934, 'miller', 'clerk', 7782, '1981-01-23', 1300, NULL, 10);

CREATE TABLE salgrade(
grade INT,
losal DOUBLE,
hisal DOUBLE
);

INSERT INTO salgrade VALUES(1,700,1200);
INSERT INTO salgrade VALUES(2, 1201, 1400);
INSERT INTO salgrade VALUES(3, 1401, 2000);
INSERT INTO salgrade VALUES(4, 2001, 3000);
INSERT INTO salgrade VALUES(5, 3001, 9999);

练习题

• 返回拥有员工的部门名、部门号
• 工资水平多于smith的员工信息
• 返回员工和所属经理的姓名
• 返回雇员的雇用日期遭遇其经理雇佣的员工及其经理姓名
• 返回员工姓名及其所在的部门名称
• 返回从事clerk工作的员工姓名和所在部门名称
• 返回部门号及其部门的最低工资
• 返回销售（sales）所有员工的姓名
• 返回工资水平多于平均工资的员工
• 返回与scott从事相同工作的员工
• 返回与30部门员工工资水平相同的员工姓名与工资
• 返回员工工作及其从事此工作的最低工资
• 计算出员工的年薪，并且以年薪排序
• 返回工资处于第四级别的员工的姓名
• 返回工资为二等级的职员名字、部门所在地

练习题答案

-- 返回拥有员工的部门名、部门号
SELECT DISTINCT d.dname,d.deptno FROM dept d JOIN emp  e ON d.deptno = e.deptno;

-- 工资水平多于smith的员工信息
SELECT * FROM emp WHERE sal > (SELECT sal FROM emp WHERE ename='smith');

-- 返回员工和所属经理的姓名
SELECT a.ename '员工',b.ename '经理'from emp a JOIN emp b ON a.mgr = b.empno;

-- 返回雇员的雇用日期遭遇其经理雇佣的员工及其经理姓名
SELECT a.ename '员工姓名',b.ename '经理姓名' FROM emp a JOIN emp  b ON a.mgr = b.empno and a.hiredate < b.hiredate;

-- 返回员工姓名及其所在的部门名称
SELECT e.ename,d.dname FROM emp e JOIN dept d ON e.deptno= d.deptno;

-- 返回从事clerk工作的员工姓名和所在部门名称
SELECT e.ename,d.dname,e.job FROM emp e JOIN dept d ON e.deptno= d.deptno AND job = 'clerk';

-- 返回部门号及其部门的最低工资
 SELECT deptno,min(sal) FROM emp GROUP BY deptno;

-- 返回销售（sales）所有员工的姓名
SELECT b.ename FROM dept a JOIN emp b ON a.deptno=b.deptno and a.dname='sales'

-- 返回工资水平多于平均工资的员工
SELECT * FROM emp WHERE sal >(SELECT AVG(sal) FROM emp);

-- 返回与scott从事相同工作的员工
SELECT * FROM emp WHERE job = (SELECT job FROM emp WHERE ename = 'scott') and ename <>'scott';

-- 返回与30部门员工工资水平相同的员工姓名与工资
SELECT * FROM emp WHERE sal > ALL(SELECT sal FROM emp WHERE deptno = 30);

-- 返回员工工作及其从事此工作的最低工资
SELECT job , min(sal) FROM emp GROUP BY job;

-- 计算出员工的年薪，并且以年薪排序
SELECT ename,sal*12+IFNULL(comm,0) FROM emp ORDER BY(sal*12+IFNULL(comm,0))DESC;

-- 返回工资处于第四级别的员工的姓名
SELECT * FROM emp WHERE sal 
BETWEEN (SELECT losal FROM salgrade WHERE grade = 4) 
and (SELECT hisal FROM salgrade WHERE grade = 4);

-- 返回工资为二等级的职员名字、部门所在地
SELECT * FROM dept a 
JOIN emp b ON a.deptno = b.deptno 
JOIN salgrade c ON grade = 2 and b.sal >= c.losal and b.sal <= c.hisal;