宿迁网站网站建设,西安短视频培训,怎么做门户网站设计,网站开发与服务合同【MySQL】之复合查询 基本查询多表查询笛卡尔积自连接子查询单行子查询多行子查询多列子查询在from子句中使用子查询 合并查询小练习 基本查询
查询工资高于500或岗位为MANAGER的雇员#xff0c;同时还要满足他们的姓名首字母为大写的J按照部门号升序而雇员的工资降序排序使用… 【MySQL】之复合查询 基本查询多表查询笛卡尔积自连接子查询单行子查询多行子查询多列子查询在from子句中使用子查询 合并查询小练习 基本查询
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按照部门号升序而雇员的工资降序排序使用年薪进行降序排序显示工资最高的员工的名字和工作岗位显示工资高于平均工资的员工信息显示每个部门的平均工资和最高工资显示平均工资低于2000的部门号和它的平均工资显示每种岗位的雇员总数平均工资
mysql select * from emp where (sal500 or jobMANAGER) 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 (sal500 or jobMANAGER) 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*12ifnull(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 |
---------------------------------
多表查询
解决多表查询的本质就是想办法将多表转化成单表
笛卡尔积 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.deptnodept.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.deptnodept.deptno and emp.deptno10;
-----------------------------
| 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 |
------------------------
自连接
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 enameFORD);
---------------
| 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.enameFORD and e1.mgre2.empno;
---------------
| ename | empno |
---------------
| JONES | 007566 |
---------------子查询
单行子查询
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 enameFORD);
--------------------------------------------------------------------------
| 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 |
--------------------------------------------------------------------------
多行子查询
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 deptno10) 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 deptno10) and deptno ! 10) as tmp ,dept where dept.deptnotmp.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 deptno30 );
----------------------------------------------------------------------------
| 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 deptno30);
----------------------------------------------------------------------------
| 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 deptno30);
-------------------------
| 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 |
-------------------------多列子查询
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 enameSMITH) 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 |
------------------------------------------------------------------------
在from子句中使用子查询
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.deptnotmp.deptno and emp.saltmp.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.deptnot2.deptno and t1.salt2.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.deptnot2.deptno ;
----------------------------------------
| dname | loc | dept_num | deptno |
----------------------------------------
| ACCOUNTING | NEW YORK | 3 | 10 |
| RESEARCH | DALLAS | 5 | 20 |
| SALES | CHICAGO | 6 | 30 |
----------------------------------------
合并查询
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 unionunion 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 sal2500 union select * from emp where jobMANAGER;
---------------------------------------------------------------------------
| 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 sal2500
union all
select * from emp where jobMANAGER;
---------------------------------------------------------------------------
| 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 |
---------------------------------------------------------------------------小练习
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_nos.emp_no and e.hire_dates.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);
