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 |
+--------+-------+---------+------+---------------------+---------+------+--------+
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 |
+--------+-------+---------+------+---------------------+---------+------+--------+
----------------
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 |
+--------+--------+-----------+------+---------------------+---------+---------+--------+
mysql> select ename,sal,comm,sal*12+ifnull(comm,0)年薪 from emp order by 年薪 desc;
+--------+---------+---------+----------+
| ename | sal | comm | 年薪 |
+--------+---------+---------+----------+
| KING | 5000.00 | NULL | 60000.00 |
| SCOTT | 3000.00 | NULL | 36000.00 |
| FORD | 3000.00 | NULL | 36000.00 |
| JONES | 2975.00 | NULL | 35700.00 |
| BLAKE | 2850.00 | NULL | 34200.00 |
| CLARK | 2450.00 | NULL | 29400.00 |
| ALLEN | 1600.00 | 300.00 | 19500.00 |
| TURNER | 1500.00 | 0.00 | 18000.00 |
| MARTIN | 1250.00 | 1400.00 | 16400.00 |
| MILLER | 1300.00 | NULL | 15600.00 |
| WARD | 1250.00 | 500.00 | 15500.00 |
| ADAMS | 1100.00 | NULL | 13200.00 |
| JAMES | 950.00 | NULL | 11400.00 |
| SMITH | 800.00 | NULL | 9600.00 |
+--------+---------+---------+----------+
mysql> select * from emp where sal=(select max(sal) from emp);
+--------+-------+-----------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-----------+------+---------------------+---------+------+--------+
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 |
+--------+-------+-----------+------+---------------------+---------+------+--------+
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 |
+--------+-------+-----------+------+---------------------+---------+------+--------+
mysql> select deptno,max(sal)最高,format(avg(sal),2) 平均 from emp group by deptno;
+--------+---------+----------+
| deptno | 最高 | 平均 |
+--------+---------+----------+
| 10 | 5000.00 | 2,916.67 |
| 20 | 3000.00 | 2,175.00 |
| 30 | 2850.00 | 1,566.67 |
+--------+---------+----------+
mysql> select deptno,avg(sal) 平均工资 from emp group by deptno having avg(sal)<2000;
+--------+--------------+
| deptno | 平均工资 |
+--------+--------------+
| 30 | 1566.666667 |
+--------+--------------+
1 row in set (0.00 sec)
mysql> select job,count(*) 人数,format(avg(sal),2) 平均工资 from emp group by job;
+-----------+--------+--------------+
| job | 人数 | 平均工资 |
+-----------+--------+--------------+
| 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 |
+-----------+--------+--------------+
解决多表查询的本质,就是想办法将多表转化成单表
其实我们只要emp表中的deptno = dept表中的deptno字段的记录
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 |
+--------+--------+-----------+------+---------------------+---------+---------+--------+--------+------------+----------+
显示部门号为10的部门名,员工名和工资
mysql> select dname, ename ,sal from emp,dept where emp.deptno=dept.deptno and emp.deptno=10;
+------------+--------+---------+
| dname | ename | sal |
+------------+--------+---------+
| ACCOUNTING | CLARK | 2450.00 |
| ACCOUNTING | KING | 5000.00 |
| ACCOUNTING | MILLER | 1300.00 |
+------------+--------+---------+
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 emp.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 |
+--------+---------+-------+
上述的笛卡尔积是两个不同的表进行的,自连接是指在同一张表连接查询
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)
第一种:使用子查询
mysql> select empno,ename from emp where emp.empno=(select mgr from emp where ename='FORD');
+--------+-------+
| empno | ename |
+--------+-------+
| 007566 | JONES |
+--------+-------+
第二种:使用自关联
使用自连接需要给表起别名
mysql> select e2.ename, e2.empno from emp e1,emp e2 where e1.ename='FORD' and e1.mgr=e2.empno;
+-------+--------+
| ename | empno |
+-------+--------+
| JONES | 007566 |
+-------+--------+
返回一行记录的子查询
显示SMITH同一部门的员工
mysql> select * from emp where deptno=(select deptno from emp where ename='FORD');
+--------+-------+---------+------+---------------------+---------+------+--------+
| 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 |
+--------+-------+---------+------+---------------------+---------+------+--------+
返回多行记录的子查询
in关键字:
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 distinct 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 |
+-------+---------+---------+--------+
查询和10号部门的工作岗位相同的雇员的名字,岗位,工资,部门名字,但是不包含10自己的
首先将上述的查询结构当做一张临时表,再和dept表做笛卡尔积
mysql> select ename,job,sal,dname from(select ename,job,sal,deptno from emp where job in(select distinct job from emp where deptno=10) and deptno != 10) as tmp ,dept where dept.deptno=tmp.deptno;
+-------+---------+---------+----------+
| ename | job | sal | dname |
+-------+---------+---------+----------+
| SMITH | CLERK | 800.00 | RESEARCH |
| JONES | MANAGER | 2975.00 | RESEARCH |
| ADAMS | CLERK | 1100.00 | RESEARCH |
| BLAKE | MANAGER | 2850.00 | SALES |
| JAMES | CLERK | 950.00 | SALES |
+-------+---------+---------+----------+
all关键字:
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
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)
mysql> select * from emp where sal > all(select distinct 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 |
+--------+-------+-----------+------+---------------------+---------+------+--------+
any关键字:
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 ename,sal,deptno from emp where sal > any(select sal from emp where deptno=30);
+--------+---------+--------+
| ename | sal | deptno |
+--------+---------+--------+
| ALLEN | 1600.00 | 30 |
| WARD | 1250.00 | 30 |
| JONES | 2975.00 | 20 |
| MARTIN | 1250.00 | 30 |
| BLAKE | 2850.00 | 30 |
| CLARK | 2450.00 | 10 |
| SCOTT | 3000.00 | 20 |
| KING | 5000.00 | 10 |
| TURNER | 1500.00 | 30 |
| ADAMS | 1100.00 | 20 |
| FORD | 3000.00 | 20 |
| MILLER | 1300.00 | 10 |
+--------+---------+--------+
单行子查询是指子查询只返回单列,单行数据;
多行子查询是指返回单列多行数据,都是针对单列而言的;
多列子查询则是指查询返回多个列数据的子查询语句
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 * from emp where (deptno,job)=(select deptno,job from emp where ename='SMITH') and ename!='SMITH' ;
+--------+-------+-------+------+---------------------+---------+------+--------+
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
+--------+-------+-------+------+---------------------+---------+------+--------+
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
+--------+-------+-------+------+---------------------+---------+------+--------+
子查询语句出现在from子句中。这里要用到数据查询的技巧,把一个子查询当做一个临时表使用
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
1.首先查出每个部门的平均工资,并将查询结果当做临时表tmp
2.联合查询emp表与tmp表
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 |
+--------+-------+-----------+------+---------------------+---------+--------+--------+--------+-------------+
查找每个部门工资最高的人的姓名、工资、部门、最高工资
1.首先查找每个部门的最高工资 t2
2.根据条件查找每个部门工资最高的人
mysql> select deptno,max(sal) mymax from emp group by deptno;
+--------+---------+
| deptno | mymax |
+--------+---------+
| 10 | 5000.00 |
| 20 | 3000.00 |
| 30 | 2850.00 |
+--------+---------+
3 rows in set (0.00 sec)
mysql> select ename,sal,t1.deptno,mymax from emp t1,
(select deptno,max(sal) mymax from emp group by deptno) t2
where t1.deptno=t2.deptno and t1.sal=t2.mymax ;
+-------+---------+--------+---------+
| ename | sal | deptno | mymax |
+-------+---------+--------+---------+
| BLAKE | 2850.00 | 30 | 2850.00 |
| SCOTT | 3000.00 | 20 | 3000.00 |
| KING | 5000.00 | 10 | 5000.00 |
| FORD | 3000.00 | 20 | 3000.00 |
+-------+---------+--------+---------+
显示每个部门的信息(部门名,编号,地址)和人员数量
1.首先找出每个部门的人员数量组成临时表t2
2.将t2作为查询表,组合查询
mysql> select t1.dname,t1.loc,t2.dept_num,t1.deptno from dept t1,
(select deptno, count(*) dept_num frrom 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 |
+------------+----------+----------+--------+
在实际应用中,为了合并多个select的执行结果,可以使用集合操作符 union,union all
union:该操作符用于取得两个结果集的并集。当使用该操作符时,会自动去掉结果集中的重复行
将工资大于2500或职位是MANAGER的人找出来
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 |
+-------+-------+-----------+------+---------------------+---------+------+--------+
union all:该操作符用于取得两个结果集的并集。当使用该操作符时,不会去掉结果集中的重复行。
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 |
+-------+-------+-----------+------+---------------------+---------+------+--------+
查找所有员工入职时候的薪水情况
select s.emp_no,s.salary
from salaries s,employees e
where e.emp_no=s.emp_no and e.hire_date=s.from_date
order by e.emp_no desc;
获取所有非manager的员工emp_no
select emp_no from employees
where emp_no not in(select emp_no from dept_manager);