- 子查询
DROP DATABASE mydb2;
USE mydb1;
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;
SELECT * FROM dept;
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 MAX(sal) FROM emp WHERE deptno=10);
SELECT * FROM emp WHERE sal>ALL(SELECT sal FROM emp WHERE 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 a 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 ename,dname FROM emp,dept WHERE emp.`deptno`=dept.`deptno` ORDER BY ename ASC;
-- from 后面接子查询
-- 查询emp表中经理信息
SELECT * FROM emp WHERE job='MANAGER';
-- 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 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
-- 工资高于30号部门所有人的员工信息 -----自行完成哟！
-- 查询工作和工资与MARTIN完全相同的员工信息
SELECT * FROM emp WHERE (sal,job) IN(SELECT sal,job FROM emp WHERE ename='MARTIN') AND ename != 'MARTIN';
-- 有两个以上直接下属的员工信息
-- 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 ---动动手美滋滋
-- 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;
SELECT * FROM dept;
SELECT deptno,AVG(sal) FROM emp GROUP BY deptno;
SELECT * FROM emp a WHERE sal>(SELECT AVG(sal) FROM emp b WHERE a.`deptno`=b.`deptno` GROUP BY b.`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 WHERE sal >(SELECT AVG(sal) FROM emp WHERE deptno=(SELECT deptno FROM dept WHERE loc='NEW YORK'))
AND deptno=(SELECT deptno FROM dept WHERE loc='DALLAS');
3. 查询7369员工编号,姓名,经理编号和经理姓名
DESC emp;
SELECT e.empno,e.ename,mar.empno,mar.ename FROM emp e, emp mar WHERE e.empno=7369 AND e.deptno=mar.`deptno`AND mar.`job`='MANAGER' ;
4. 查询出各个部门薪水最高的员工所有信息
SELECT * FROM emp a WHERE sal=(SELECT MAX(sal) FROM emp b WHERE a.deptno=b.deptno 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语句查出分数大于80的学生
SELECT DISTINCT NAME FROM test WHERE fenshu >80;
SELECT DISTINCT NAME FROM test WHERE NAME NOT IN(SELECT NAME FROM test WHERE fenshu<=80);