SQ多表查询练习

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
) ;

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);




CREATE TABLE dept(
	deptno		INT,
	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');

单行子查询(> < >= <= = <>)
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) and deptno!=10;

多行子查询(in not in any all)
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>any(select sal from emp where deptno=10) and deptno!=10;

多列子查询(实际使用较少
和10号部门同名同工作的员工信息

select * from emp where (ename,job) in(select ename,job from emp where deptno=10) and deptno!=10;

select 后面接子查询
获取员工的名字和部门的名字

select e.ename,d.dname from emp e,dept d where e.deptno=d.deptno;

from 后面接子查询
查询emp表中经理信息

select * from emp e,(select distinct mgr from emp) as jingli whereE e.empno=jingli.mgr;

where 后面接子查询
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 where deptno=10) and deptno!=10;

group by 后面接子查询
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) as bumen from emp group by deptno having bumen > (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=(select deptno from emp where ename='SCOTT') and ename!='SCOTT';

工资高于30号部门所有人的员工信息

select * from emp where sal>all(select sal from emp where deptno=30);

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 ename="MARTIN") and job=(select job from emp where 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) >2);

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 emp e,dept d where e.empno=7788 and d.deptno=e.deptno;

SQL查询的综合案例

1. 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) as 平均工资 from emp d group by deptno having e.deptno=d.deptno);

2. 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 where e.deptno=(select d.deptno from dept d where d.loc="DALLAS") and e.sal>(select avg(e.sal) from emp e where e.deptno=(select d.deptno from dept d where d.loc="NEW YORK"));

3. 查询7369员工编号,姓名,经理编号和经理姓名

select e1.empno,e1.ename,e1.mgr,e2.ename from emp e1,emp e2 where e1.mgr = e2.empno and e1.empno = 7369;

4. 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 d where d.deptno=e.deptno);