– 子查询
CREATE TABLE emp(– emp表是employee雇员信息表
empno INT,– empno就是雇员的员工编号，employee number
ename VARCHAR(50),– ename员工姓名，emlployee name
job VARCHAR(50),– job员工的工作是什么比如推销员，经理等
mgr INT,– mgr.上级编号
hiredate DATE,– hiredate受雇日期
sal DECIMAL(7,2),– sal薪金
comm DECIMAL(7,2),– comm佣金
deptno INT – deptno部门编号
) ;
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);
– 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>(select MIN(sal) from emp where deptno=10) and deptno not in(10);
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 where job=‘manager’;
SELECT * FROM emp e,(SELECT DISTINCT mgr FROM emp) AS jingli WHERE 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);
– 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 AVG(sal),deptno from emp GROUP BY deptno HAVING AVG(sal)>(select AVG(sal) from emp where deptno=30);
– 工资>JONES工资
– 查询与SCOTT同一个部门的员工
select * from emp where deptno=(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 MAX(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 job,sal from emp where ename=‘MARTIN’
select * from emp where job=(select job from emp where ename=‘MARTIN’) and sal=(select sal from emp where ename=‘MARTIN’) and ename not in(‘MARTIN’);
######– 有两个以上直接下属的员工信息
select * from emp where (select count(*), from emp GROUP BY 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.deptno=d.deptno and e.empno=7788;
– 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 where sal>(select avg(sal) from emp GROUP BY deptno)
– 2. 列出达拉斯加工作的人中,比纽约平均工资高的人
– 3. 查询7369员工编号,姓名,经理编号和经理姓名
select empno,ename,mgr,(select ename from emp where empno=(select mgr from emp where empno=7369)) mgrname from emp where empno=7369;
######– 4. 查询出各个部门薪水最高的员工所有信息
select avg(sal) from emp GROUP BY deptno
面试题
CREATE TABLE test(
NAME CHAR(20),
kecheng CHAR(20),
fenshu CHAR(20)
);
INSERT INTO test VALUES(‘张三’,‘语文’,81),
(‘张三’,‘数学’,75),
(‘李四’,‘语文’,76),
(‘李四’,‘数学’,90),
(‘王五’,‘语文’,81),
(‘王五’,‘数学’,82);
– 请用一条Sql语句查处分数大于80的学生
select * from test where fenshu>80;