文章目录
- 复合查询
- 多表查询
- 子查询 (嵌套查询)
- 多列子查询
- 合并查询
复合查询
查询工资高于500或岗位为MANAGER的雇员，同时还要满足他们的姓名首字母为大写的J
mysql> select * from emp where (sal>500 or job ='MANAGER') and ename like 'J%' ;
+--------+-------+---------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+---------+------+---------------------+---------+------+--------+
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 |
+--------+-------+---------+------+---------------------+---------+------+--------+
2 rows in set (0.00 sec)mysql> select * from emp where (sal>500 or job ='MANAGER') and substring(ename,1,1) ='J' ;
+--------+-------+---------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+---------+------+---------------------+---------+------+--------+
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 |
+--------+-------+---------+------+---------------------+---------+------+--------+
2 rows in set (0.01 sec)按照部门号升序而雇员的工资降序排序
mysql> select * from emp order by deptno asc ,sal desc;
+--------+--------+-----------+------+---------------------+---------+---------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+--------+-----------+------+---------------------+---------+---------+--------+
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 |
+--------+--------+-----------+------+---------------------+---------+---------+--------+
14 rows in set (0.00 sec)使用年薪进行降序排序
mysql> select sal*12 + ifnull(comm,0) 年薪 from emp order by 年薪 desc ;
+----------+
| 年薪 |
+----------+
| 60000.00 |
| 36000.00 |
| 36000.00 |
| 35700.00 |
| 34200.00 |
| 29400.00 |
| 19500.00 |
| 18000.00 |
| 16400.00 |
| 15600.00 |
| 15500.00 |
| 13200.00 |
| 11400.00 |
| 9600.00 |
+----------+
14 rows in set (0.00 sec)显示工资最高的员工的名字和工作岗位
mysql> select ename,job from emp where sal=(select max(sal) from emp) ;
+-------+-----------+
| ename | job |
+-------+-----------+
| KING | PRESIDENT |
+-------+-----------+
1 row in set (0.00 sec)显示工资高于平均工资的员工信息
mysql> select * from emp where sal > (select avg(sal) from emp ) ;
+--------+-------+-----------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-----------+------+---------------------+---------+------+--------+
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
+--------+-------+-----------+------+---------------------+---------+------+--------+
6 rows in set (0.00 sec)显示每个部门的平均工资和最高工资
mysql> select deptno , format(max(sal),2) ,format( avg(sal),2) from emp group by deptno ;
+--------+--------------------+---------------------+
| deptno | format(max(sal),2) | format( avg(sal),2) |
+--------+--------------------+---------------------+
| 10 | 5,000.00 | 2,916.67 |
| 20 | 3,000.00 | 2,175.00 |
| 30 | 2,850.00 | 1,566.67 |
+--------+--------------------+---------------------+
3 rows in set (0.00 sec)显示平均工资低于2000的部门号和它的平均工资
mysql> select deptno ,avg(sal) 平均工资 from emp group by deptno having 平均工资<2000 ;
+--------+--------------+
| deptno | 平均工资 |
+--------+--------------+
| 30 | 1566.666667 |
+--------+--------------+
1 row in set (0.00 sec)显示每种岗位的雇员总数，平均工资
mysql> select job ,count(*) 人数, format (avg(sal) ,2) 平均 from emp group by job ;
+-----------+--------+----------+
| job | 人数 | 平均 |
+-----------+--------+----------+
| ANALYST | 2 | 3,000.00 |
| CLERK | 4 | 1,037.50 |
| MANAGER | 3 | 2,758.33 |
| PRESIDENT | 1 | 5,000.00 |
| SALESMAN | 4 | 1,400.00 |
+-----------+--------+----------+
5 rows in set (0.00 sec)多表查询
显示雇员名、雇员工资以及所在部门的名字因为上面的数据来自EMP和DEPT表，因此要联合查询
mysql> select ename ,sal ,dname from emp ,dept where emp.deptno=dept.deptno;
+--------+---------+------------+
| ename | sal | dname |
+--------+---------+------------+
| SMITH | 800.00 | RESEARCH |
| ALLEN | 1600.00 | SALES |
| WARD | 1250.00 | SALES |
| JONES | 2975.00 | RESEARCH |
| MARTIN | 1250.00 | SALES |
| BLAKE | 2850.00 | SALES |
| CLARK | 2450.00 | ACCOUNTING |
| SCOTT | 3000.00 | RESEARCH |
| KING | 5000.00 | ACCOUNTING |
| TURNER | 1500.00 | SALES |
| ADAMS | 1100.00 | RESEARCH |
| JAMES | 950.00 | SALES |
| FORD | 3000.00 | RESEARCH |
| MILLER | 1300.00 | ACCOUNTING |
+--------+---------+------------+
14 rows in set (0.00 sec)显示部门号为10的部门名，员工名和工资
mysql> select ename, sal ,dname,dept.deptno from emp ,dept where emp.deptno= dept.deptno and emp.deptno=10;
+--------+---------+------------+--------+
| ename | sal | dname | deptno |
+--------+---------+------------+--------+
| CLARK | 2450.00 | ACCOUNTING | 10 |
| KING | 5000.00 | ACCOUNTING | 10 |
| MILLER | 1300.00 | ACCOUNTING | 10 |
+--------+---------+------------+--------+
3 rows in set (0.00 sec)显示各个员工的姓名，工资，及工资级别
mysql> select ename ,sal ,grade from emp , salgrade where sal between losal and hisal;
+--------+---------+-------+
| ename | sal | grade |
+--------+---------+-------+
| SMITH | 800.00 | 1 |
| ALLEN | 1600.00 | 3 |
| WARD | 1250.00 | 2 |
| JONES | 2975.00 | 4 |
| MARTIN | 1250.00 | 2 |
| BLAKE | 2850.00 | 4 |
| CLARK | 2450.00 | 4 |
| SCOTT | 3000.00 | 4 |
| KING | 5000.00 | 5 |
| TURNER | 1500.00 | 3 |
| ADAMS | 1100.00 | 1 |
| JAMES | 950.00 | 1 |
| FORD | 3000.00 | 4 |
| MILLER | 1300.00 | 2 |
+--------+---------+-------+
14 rows in set (0.00 sec)# 自连接
显示员工FORD的上级领导的编号和姓名（mgr是员工领导的编号–empno）
1、子查询
mysql> select ename ,empno from emp where empno =(select mgr from emp where ename ='FORD') ;
+-------+--------+
| ename | empno |
+-------+--------+
| JONES | 007566 |
+-------+--------+
1 row in set (0.00 sec)2、自连接
对同一张表进行笛卡尔积，然后进行筛选信息
mysql> select e2.ename, e2.empno from emp e1 , emp e2 where e1.ename='FORD' and e1.mgr = e2.empno ;
+-------+--------+
| ename | empno |
+-------+--------+
| JONES | 007566 |
+-------+--------+
1 row in set (0.00 sec)子查询 (嵌套查询)
单行子查询：
先执行括号内部的查询 ，再执行括号外的查询
显示SMITH同一部门的员工
mysql> select * from emp where deptno=(select deptno from emp where ename ='SMITH');
+--------+-------+---------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+---------+------+---------------------+---------+------+--------+
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
+--------+-------+---------+------+---------------------+---------+------+--------+
5 rows in set (0.00 sec)多行子查询：
查询和10号部门的工作岗位相同的雇员的名字，岗位，工资，部门号，但是不包含10自
己的
mysql> select ename,job,sal,deptno from emp where job in(select job from emp where deptno =10 ) and deptno !=10 ;
+-------+---------+---------+--------+
| ename | job | sal | deptno |
+-------+---------+---------+--------+
| JONES | MANAGER | 2975.00 | 20 |
| BLAKE | MANAGER | 2850.00 | 30 |
| SMITH | CLERK | 800.00 | 20 |
| ADAMS | CLERK | 1100.00 | 20 |
| JAMES | CLERK | 950.00 | 30 |
+-------+---------+---------+--------+
5 rows in set (0.00 sec)显示工资比部门30的所有员工的工资高的员工的姓名、工资和部门号
第一种写法
mysql> select max(sal) from emp where deptno=30 ;
+----------+
| max(sal) |
+----------+
| 2850.00 |
+----------+
1 row in set (0.00 sec)mysql> select * from emp where sal> (select max(sal) from emp where deptno=30 ) ;
+--------+-------+-----------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-----------+------+---------------------+---------+------+--------+
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
+--------+-------+-----------+------+---------------------+---------+------+--------+
4 rows in set (0.00 sec)第二种写法
mysql> select sal from emp where deptno=30 ;
+---------+
| sal |
+---------+
| 1600.00 |
| 1250.00 |
| 1250.00 |
| 2850.00 |
| 1500.00 |
| 950.00 |
+---------+
6 rows in set (0.00 sec)mysql> select * from emp where sal>all ( select sal from emp where deptno=30) ;
+--------+-------+-----------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-----------+------+---------------------+---------+------+--------+
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
+--------+-------+-----------+------+---------------------+---------+------+--------+
4 rows in set (0.00 sec)显示工资比部门30的任意员工的工资高的员工的姓名、工资和部门号（包含自己部门的员工）
mysql> select distinct sal from emp where deptno =30;
+---------+
| sal |
+---------+
| 1600.00 |
| 1250.00 |
| 2850.00 |
| 1500.00 |
| 950.00 |
+---------+
5 rows in set (0.00 sec)mysql> select * from emp where sal>any(select distinct sal from emp where deptno =30 );
+--------+--------+-----------+------+---------------------+---------+---------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+--------+-----------+------+---------------------+---------+---------+--------+
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 |
+--------+--------+-----------+------+---------------------+---------+---------+--------+
12 rows in set (0.00 sec)多列子查询
查询和SMITH的部门和岗位完全相同的所有雇员，不含SMITH本人
mysql> select deptno ,job from emp where ename ='SMITH';
+--------+-------+
| deptno | job |
+--------+-------+
| 20 | CLERK |
+--------+-------+
1 row in set (0.00 sec)mysql> select * from emp where (deptno ,job) = (select deptno ,job from emp where ename ='SMITH') ;
+--------+-------+-------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-------+------+---------------------+---------+------+--------+
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
+--------+-------+-------+------+---------------------+---------+------+--------+
2 rows in set (0.00 sec)mysql> select * from emp where (deptno ,job) = (select deptno ,job from emp where ename ='SMITH')andename !='SMITH' ;
+--------+-------+-------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-------+------+---------------------+---------+------+--------+
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
+--------+-------+-------+------+---------------------+---------+------+--------+
1 row in set (0.00 sec)目前全部的子查询，全部都在where子句中，充当判断条件
显示每个高于自己部门平均工资的员工的姓名、部门、工资、平均工资
mysql> select deptno , avg(sal) from emp group by deptno ;
+--------+-------------+
| deptno | avg(sal) |
+--------+-------------+
| 10 | 2916.666667 |
| 20 | 2175.000000 |
| 30 | 1566.666667 |
+--------+-------------+
3 rows in set (0.00 sec)mysql> select * from emp ,( select deptno , avg(sal) from emp group by deptno ) tmp where emp.deptno=tmp.deptno ;
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+-------------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | deptno | avg(sal) |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+-------------+
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 | 20 | 2175.000000 |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 30 | 1566.666667 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 | 30 | 1566.666667 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 20 | 2175.000000 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 | 30 | 1566.666667 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 30 | 1566.666667 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 | 10 | 2916.666667 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 20 | 2175.000000 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 10 | 2916.666667 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 | 30 | 1566.666667 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 | 20 | 2175.000000 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 | 30 | 1566.666667 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 20 | 2175.000000 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 | 10 | 2916.666667 |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+-------------+
14 rows in set (0.00 sec)mysql> select * from emp ,( select deptno , avg(sal) myavg from emp group by deptno ) tmp where emp.deptno=tmp.deptno and emp.sal > tmp.myavg ;
+--------+-------+-----------+------+---------------------+---------+--------+--------+--------+-------------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | deptno | myavg |
+--------+-------+-----------+------+---------------------+---------+--------+--------+--------+-------------+
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 30 | 1566.666667 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 20 | 2175.000000 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 30 | 1566.666667 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 20 | 2175.000000 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 10 | 2916.666667 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 20 | 2175.000000 |
+--------+-------+-----------+------+---------------------+---------+--------+--------+--------+-------------+
6 rows in set (0.00 sec)查找每个部门工资最高的人的姓名、工资、部门、最高工资
mysql> select deptno , max(sal) from emp group by deptno ;
+--------+----------+
| deptno | max(sal) |
+--------+----------+
| 10 | 5000.00 |
| 20 | 3000.00 |
| 30 | 2850.00 |
+--------+----------+
3 rows in set (0.00 sec)mysql> select * from emp t1 , (select deptno , max(sal) from emp group by deptno )t2;
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+----------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | deptno | max(sal) |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+----------+
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 | 10 | 5000.00 |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 10 | 5000.00 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 | 10 | 5000.00 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 10 | 5000.00 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 | 10 | 5000.00 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 10 | 5000.00 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 | 10 | 5000.00 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 10 | 5000.00 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 10 | 5000.00 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 | 10 | 5000.00 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 | 10 | 5000.00 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 | 10 | 5000.00 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 10 | 5000.00 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 | 10 | 5000.00 |
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 | 20 | 3000.00 |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 20 | 3000.00 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 | 20 | 3000.00 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 20 | 3000.00 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 | 20 | 3000.00 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 20 | 3000.00 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 | 20 | 3000.00 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 20 | 3000.00 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 20 | 3000.00 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 | 20 | 3000.00 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 | 20 | 3000.00 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 | 20 | 3000.00 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 20 | 3000.00 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 | 20 | 3000.00 |
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 | 30 | 2850.00 |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 30 | 2850.00 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 | 30 | 2850.00 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 30 | 2850.00 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 | 30 | 2850.00 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 30 | 2850.00 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 | 30 | 2850.00 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 30 | 2850.00 |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 30 | 2850.00 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 | 30 | 2850.00 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 | 30 | 2850.00 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 | 30 | 2850.00 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 30 | 2850.00 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 | 30 | 2850.00 |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+----------+
42 rows in set (0.00 sec)mysql> select ename,sal,t1.deptno from emp t1 , (select deptno , max(sal) mymax from emp group by depptno )t2 where t1.deptno=t2.deptno and t1.sal =t2.mymax ;
+-------+---------+--------+
| ename | sal | deptno |
+-------+---------+--------+
| BLAKE | 2850.00 | 30 |
| SCOTT | 3000.00 | 20 |
| KING | 5000.00 | 10 |
| FORD | 3000.00 | 20 |
+-------+---------+--------+
4 rows in set (0.00 sec)显示每个部门的信息（部门名，编号，地址）和人员数量
方法1：使用子查询
mysql> select deptno , count(*) dept_num from emp group by deptno ;
+--------+----------+
| deptno | dept_num |
+--------+----------+
| 10 | 3 |
| 20 | 5 |
| 30 | 6 |
+--------+----------+
3 rows in set (0.00 sec)mysql> select * from dept t1, ( select deptno , count(*) dept_num from emp group by deptno) t2 ;+--------+------------+----------+--------+----------+
| deptno | dname | loc | deptno | dept_num |
+--------+------------+----------+--------+----------+
| 10 | ACCOUNTING | NEW YORK | 10 | 3 |
| 20 | RESEARCH | DALLAS | 10 | 3 |
| 30 | SALES | CHICAGO | 10 | 3 |
| 40 | OPERATIONS | BOSTON | 10 | 3 |
| 10 | ACCOUNTING | NEW YORK | 20 | 5 |
| 20 | RESEARCH | DALLAS | 20 | 5 |
| 30 | SALES | CHICAGO | 20 | 5 |
| 40 | OPERATIONS | BOSTON | 20 | 5 |
| 10 | ACCOUNTING | NEW YORK | 30 | 6 |
| 20 | RESEARCH | DALLAS | 30 | 6 |
| 30 | SALES | CHICAGO | 30 | 6 |
| 40 | OPERATIONS | BOSTON | 30 | 6 |
+--------+------------+----------+--------+----------+
12 rows in set (0.00 sec)mysql> select * from dept t1, ( select deptno , count(*) dept_num from emp group by deptno) t2 where t1.deptno = t2.deptno ;
+--------+------------+----------+--------+----------+
| deptno | dname | loc | deptno | dept_num |
+--------+------------+----------+--------+----------+
| 10 | ACCOUNTING | NEW YORK | 10 | 3 |
| 20 | RESEARCH | DALLAS | 20 | 5 |
| 30 | SALES | CHICAGO | 30 | 6 |
+--------+------------+----------+--------+----------+
3 rows in set (0.00 sec)
mysql> select t1.dname ,t1.loc,t2.dept_num,t1.deptno from dept t1, ( select deptno , count(*) dept_nnum from emp group by deptno) t2 where t1.deptno = t2.deptno ;
+------------+----------+----------+--------+
| dname | loc | dept_num | deptno |
+------------+----------+----------+--------+
| ACCOUNTING | NEW YORK | 3 | 10 |
| RESEARCH | DALLAS | 5 | 20 |
| SALES | CHICAGO | 6 | 30 |
+------------+----------+----------+--------+
3 rows in set (0.00 sec)方法2：使用多表
mysql> select * from emp ,dept where emp.deptno =dept.deptno ;
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+------------+----------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno | deptno | dname | loc |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+------------+----------+
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 | 20 | RESEARCH | DALLAS |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 30 | SALES | CHICAGO |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 | 30 | SALES | CHICAGO |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 20 | RESEARCH | DALLAS |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 | 30 | SALES | CHICAGO |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 30 | SALES | CHICAGO |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 | 10 | ACCOUNTING | NEW YORK |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 20 | RESEARCH | DALLAS |
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 10 | ACCOUNTING | NEW YORK |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 | 30 | SALES | CHICAGO |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 | 20 | RESEARCH | DALLAS |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 | 30 | SALES | CHICAGO |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 20 | RESEARCH | DALLAS |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 | 10 | ACCOUNTING | NEW YORK |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+------------+----------+
14 rows in set (0.00 sec)mysql> select emp.deptno, count(*) from emp ,dept where emp.deptno =dept.deptno group by emp.deptno ;+--------+----------+
| deptno | count(*) |
+--------+----------+
| 10 | 3 |
| 20 | 5 |
| 30 | 6 |
+--------+----------+
3 rows in set (0.00 sec)mysql> select emp.deptno,dept.dname,dept.loc, count(*) from emp ,dept where emp.deptno =dept.deptno grroup by emp.deptno ,dept.dname,dept.loc;
+--------+------------+----------+----------+
| deptno | dname | loc | count(*) |
+--------+------------+----------+----------+
| 10 | ACCOUNTING | NEW YORK | 3 |
| 20 | RESEARCH | DALLAS | 5 |
| 30 | SALES | CHICAGO | 6 |
+--------+------------+----------+----------+
3 rows in set (0.00 sec)合并查询
将工资大于2500或职位是MANAGER的人找出来
去重：
mysql> select * from emp where sal > 2500 union select * from emp where job='MANAGER ' ;
+-------+-------+-----------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+-------+-----------+------+---------------------+---------+------+--------+
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 |
+-------+-------+-----------+------+---------------------+---------+------+--------+
6 rows in set (0.00 sec)不去重：
mysql> select * from emp where sal > 2500 union all select * from emp where job='MANAGER ' ;
+-------+-------+-----------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+-------+-------+-----------+------+---------------------+---------+------+--------+
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 |
| 7788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 |
| 7839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
| 7902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 |
| 7566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 |
| 7698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 |
| 7782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 |
+-------+-------+-----------+------+---------------------+---------+------+--------+
8 rows in set (0.00 sec)
