MySQL子查询学习(练习)

CREATE TABLE emp(
empno  INT,
ename  VARCHAR(50),
job  VARCHAR(50),
mgr  INT,
hiredate DATE,
sal  DECIMAL(7,2),
comm  DECIMAL(7,2),
deptno  INT
) ;
CREATE TABLE dept(
deptno  INT,
dname  VARCHAR(14),
loc
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,'1981-02-22',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,'BLAKE','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,'1987-04-19',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,'1987-05-23',1100,NULL,20);
INSERT INTO emp VALUES(7900,'JAMES','CLERK',7698,'1981-12-03',950,NULL,30);
INSERT INTO emp VALUES(7902,'FORD','ANALYST',7566,'1981-12-03',3000,NULL,20);
INSERT INTO emp VALUES(7934,'MILLER','CLERK',7782,'1982-01-23',1300,NULL,10);

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');
SELECT *FROM emp
-- 查询出高于10号部门的平均工资的员工信息
SELECT * FROM emp WHERE sal>(SELECT AVG(sal) FROM emp WHERE deptno=10)
-- 查询出比10号部门任何员工薪资高的员工信息
SELECT * FROM emp WHERE sal>(SELECT sal FROM emp WHERE deptno=10 ORDER BY sal LIMIT 1)
-- 和10号部门同名同工作的员工信息
SELECT * FROM emp WHERE deptno IN(20,30,40)AND (ename=(SELECT ename FROM emp)AND job=(SELECT job FROM emp))
-- 获取员工的名字和部门的名字
SELECT e.ename,d.dname FROM emp e INNER JOIN dept d ON e.deptno=d.deptno
-- 查询emp表中经理信息
SELECT a.* FROM (SELECT * FROM emp WHERE job='MANAGER') a
-- 薪资高于10号部门平均工资的所有员工信息
SELECT * FROM emp WHERE sal>(SELECT AVG(sal) FROM emp GROUP BY deptno HAVING deptno=10)
-- 有哪些部门的平均工资高于30号部门的平均工资
SELECT deptno,AVG(sal) avgsal FROM emp GROUP BY deptno HAVING avgsal>(SELECT AVG(sal) FROM emp WHERE deptno=30)
-- 工资>JONES工资
SELECT * FROM emp WHERE sal>(SELECT sal FROM emp WHERE ename='JONES')
-- 查询与SCOTT同一个部门的员工
SELECT * FROM emp WHERE deptno IN(SELECT deptno FROM emp WHERE ename='SCOTT')
-- 工资高于30号部门所有人的员工信息
SELECT * FROM emp WHERE sal>(SELECT sal FROM emp WHERE deptno=30 ORDER BY sal DESC LIMIT 1)
-- 查询工作和工资与MARTIN完全相同的员工信息
SELECT * FROM emp WHERE sal=(SELECT sal FROM emp WHERE job=(SELECT job FROM emp WHERE ename='MARTIN')AND ename='MARTIN')
-- 有两个以上直接下属的员工信息
SELECT * FROM emp WHERE empno IN(SELECT mgr FROM emp GROUP BY mgr HAVING COUNT(mgr)>1)
-- 查询员工编号为7788的员工名称,员工工资,部门名称,部门地址
SELECT e.ename,e.sal,d.dname,d.loc FROM dept d INNER JOIN (SELECT * FROM emp) e ON d.deptno=e.deptno WHERE e.empno='7788'
--  查询出高于本部门平均工资的员工信息
SELECT * FROM emp e WHERE sal>(SELECT AVG(sal) FROM emp GROUP BY deptno HAVING deptno=e.deptno)
--. 列出达拉斯加工作的人中,比纽约平均工资高的人
SELECT * FROM emp e INNER JOIN dept d ON e.deptno=d.deptno WHERE e.sal>(SELECT AVG(sal) FROM emp e INNER JOIN dept d ON e.deptno=d.deptno WHERE d.loc='NEW YORK')AND d.loc='DALLAS'
-- 查询7369员工编号,姓名,经理编号和经理姓名
SELECT e.empno 编号,e.ename 姓名,m.empno 经理编号,m.ename 经理姓名 FROM emp m INNER JOIN (SELECT * FROM emp WHERE empno='7369') e ON m.deptno=e.deptno WHERE m.empno=e.mgr
--  查询出各个部门薪水最高的员工所有信息
SELECT * FROM emp e WHERE sal=(SELECT MAX(sal) FROM emp GROUP BY deptno HAVING deptno=e.deptno)
-- 如果有需要解释的留下评论，代码太多无法都解释了，我还在上学没有时间，抱歉抱歉有时间解释我会慢慢更新的
--评论带这题就行了