wordpress激活码注册插件,襄樊seo快速排名,网站建设班,dede 网站地图 模块1. 整体学习的思维导图 2. 回顾基本查询
使用scott数据库中的表#xff0c;完成以下查询#xff1a; 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
mysql select * from emp where (sal500 or jobMANAGER) and ename …
1. 整体学习的思维导图 2. 回顾基本查询
使用scott数据库中的表完成以下查询 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 (sal500 or jobMANAGER) and ename likeJ%;
--------------------------------------------------------------------------
| 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 |
-------------------------------------------------------------------------- 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 |
-------------------------------------------------------------------------------- 使用年薪进行降序排序
mysql select *,sal*12ifnull(comm,0) 年薪 from emp order by 年薪 desc;
------------------------------------------------------------------------------------------
| empno | ename | job | mgr | hiredate | sal | comm | deptno | 年薪 |
------------------------------------------------------------------------------------------
| 007839 | KING | PRESIDENT | NULL | 1981-11-17 00:00:00 | 5000.00 | NULL | 10 | 60000.00 |
| 007788 | SCOTT | ANALYST | 7566 | 1987-04-19 00:00:00 | 3000.00 | NULL | 20 | 36000.00 |
| 007902 | FORD | ANALYST | 7566 | 1981-12-03 00:00:00 | 3000.00 | NULL | 20 | 36000.00 |
| 007566 | JONES | MANAGER | 7839 | 1981-04-02 00:00:00 | 2975.00 | NULL | 20 | 35700.00 |
| 007698 | BLAKE | MANAGER | 7839 | 1981-05-01 00:00:00 | 2850.00 | NULL | 30 | 34200.00 |
| 007782 | CLARK | MANAGER | 7839 | 1981-06-09 00:00:00 | 2450.00 | NULL | 10 | 29400.00 |
| 007499 | ALLEN | SALESMAN | 7698 | 1981-02-20 00:00:00 | 1600.00 | 300.00 | 30 | 19500.00 |
| 007844 | TURNER | SALESMAN | 7698 | 1981-09-08 00:00:00 | 1500.00 | 0.00 | 30 | 18000.00 |
| 007654 | MARTIN | SALESMAN | 7698 | 1981-09-28 00:00:00 | 1250.00 | 1400.00 | 30 | 16400.00 |
| 007934 | MILLER | CLERK | 7782 | 1982-01-23 00:00:00 | 1300.00 | NULL | 10 | 15600.00 |
| 007521 | WARD | SALESMAN | 7698 | 1981-02-22 00:00:00 | 1250.00 | 500.00 | 30 | 15500.00 |
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 | 13200.00 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 | 11400.00 |
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 | 9600.00 |
------------------------------------------------------------------------------------------ 显示工资最高的员工的名字和工作岗位
mysql select ename,job,sal from emp where sal(select max(sal) from emp);
---------------------------
| ename | job | sal |
---------------------------
| KING | PRESIDENT | 5000.00 |
--------------------------- 显示工资高于平均工资的员工信息
mysql select * from emp where sal(select avg(sal) mysal 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 |
---------------------------------------------------------------------------- 显示每个部门的平均工资和最高工资
mysql select deptno,format(avg(sal), 2),max(sal) from emp group by deptno;
---------------------------------------
| deptno | format(avg(sal), 2) | max(sal) |
---------------------------------------
| 10 | 2,916.67 | 5000.00 |
| 20 | 2,175.00 | 3000.00 |
| 30 | 1,566.67 | 2850.00 |
--------------------------------------- 显示平均工资低于2000的部门号和它的平均工资
mysql select * from (select deptno,avg(sal) myavg from emp group by deptno) tb1 where myavg 2000;
---------------------
| deptno | myavg |
---------------------
| 30 | 1566.666667 |
--------------------- 显示每种岗位的雇员总数平均工资
mysql select job,count(*),format(avg(sal), 2) myavg from emp group by job;
-------------------------------
| job | count(*) | myavg |
-------------------------------
| 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 |
-------------------------------
3. 多表查询
顾名思义就是在多个表中查询多表又分为两种情况 多表存在着明显的外键联系 多表不存在隐藏的外键联系
mysql select * from emp;
--------------------------------------------------------------------------------
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
--------------------------------------------------------------------------------
| 007369 | SMITH | CLERK | 7902 | 1980-12-17 00:00:00 | 800.00 | NULL | 20 |
| 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 |
| 007900 | JAMES | CLERK | 7698 | 1981-12-03 00:00:00 | 950.00 | NULL | 30 |
| 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 |
--------------------------------------------------------------------------------mysql select * from dept;
------------------------------
| deptno | dname | loc |
------------------------------
| 10 | ACCOUNTING | NEW YORK |
| 20 | RESEARCH | DALLAS |
| 30 | SALES | CHICAGO |
| 40 | OPERATIONS | BOSTON |
------------------------------
-- 以上就是明显的外键联系 deptnomysql select * from salgrade;
---------------------
| grade | losal | hisal |
---------------------
| 1 | 700 | 1200 |
| 2 | 1201 | 1400 |
| 3 | 1401 | 2000 |
| 4 | 2001 | 3000 |
| 5 | 3001 | 9999 |
---------------------
-- 这个表和emp的sal联系sal在losal~hisal之间决定grade这种联系比较隐藏
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 通过外键联系我们就可以去重。
mysql select ename,sal,dname from emp,dept where emp.deptnodept.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 |
-----------------------------
显示部门号为10的部门名员工名和工资
mysql select emp.deptno,dname,ename,sal from emp,dept where emp.deptnodept.deptno and emp.deptno10;
-------------------------------------
| deptno | dname | ename | sal |
-------------------------------------
| 10 | ACCOUNTING | CLARK | 2450.00 |
| 10 | ACCOUNTING | KING | 5000.00 |
| 10 | ACCOUNTING | MILLER | 1300.00 |
-------------------------------------
显示各个员工的姓名工资及工资级别
mysql select emp.ename,emp.sal,salgrade.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 |
------------------------
4. 自连接
自连接是指在同一张表连接查询案例 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 子查询
mysql select empno,ename from emp where empno(select mgr from emp where enameFORD);
---------------
| empno | ename |
---------------
| 007566 | JONES |
--------------- 多表查询
mysql select leader.empno,leader.ename from emp leader,emp worker where leader.empno worker.mgr and worker.enameFORD;
---------------
| empno | ename |
---------------
| 007566 | JONES |
---------------
5. 子查询
又称作为嵌套查询就是在select语句中再次嵌套select
5.1 单行子查询
指嵌套语句中返回单个子查询结果如下面问题的deptno 显示SMITH同一部门的员工
mysql select deptno,ename from emp where deptno(select deptno from emp where enameSMITH);
---------------
| deptno | ename |
---------------
| 20 | SMITH |
| 20 | JONES |
| 20 | SCOTT |
| 20 | ADAMS |
| 20 | FORD |
---------------
5.2 多行子查询
指嵌套语句中返回多个子查询结果 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 job from emp where deptno10) and deptno10;
---------------------------------
| 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 |
---------------------------------
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 ename,sal,deptno from emp where sal all(select sal from emp where deptno30);
------------------------
| ename | sal | deptno |
------------------------
| JONES | 2975.00 | 20 |
| SCOTT | 3000.00 | 20 |
| KING | 5000.00 | 10 |
| FORD | 3000.00 | 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、工资和部门号不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) and deptno30;
-------------------------
| ename | sal | deptno |
-------------------------
| JONES | 2975.00 | 20 |
| CLARK | 2450.00 | 10 |
| SCOTT | 3000.00 | 20 |
| KING | 5000.00 | 10 |
| ADAMS | 1100.00 | 20 |
| FORD | 3000.00 | 20 |
| MILLER | 1300.00 | 10 |
-------------------------
5.3 多列子查询
查询的条件有多个返回多列条件 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 enameSMITH;
------------------------------------------------------------------------
| empno | ename | job | mgr | hiredate | sal | comm | deptno |
------------------------------------------------------------------------
| 007876 | ADAMS | CLERK | 7788 | 1987-05-23 00:00:00 | 1100.00 | NULL | 20 |
------------------------------------------------------------------------
5.4 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
mysql select ename,emp.deptno,sal,tmp.avgsal from emp,(select deptno,avg(sal) avgsal from emp group by deptno) tmp where emp.sal tmp.avgsal;
-------------------------------------
| ename | deptno | sal | avgsal |
-------------------------------------
| JONES | 20 | 2975.00 | 2916.666667 |
| SCOTT | 20 | 3000.00 | 2916.666667 |
| KING | 10 | 5000.00 | 2916.666667 |
| FORD | 20 | 3000.00 | 2916.666667 |
| JONES | 20 | 2975.00 | 2175.000000 |
| BLAKE | 30 | 2850.00 | 2175.000000 |
| CLARK | 10 | 2450.00 | 2175.000000 |
| SCOTT | 20 | 3000.00 | 2175.000000 |
| KING | 10 | 5000.00 | 2175.000000 |
| FORD | 20 | 3000.00 | 2175.000000 |
| ALLEN | 30 | 1600.00 | 1566.666667 |
| JONES | 20 | 2975.00 | 1566.666667 |
| BLAKE | 30 | 2850.00 | 1566.666667 |
| CLARK | 10 | 2450.00 | 1566.666667 |
| SCOTT | 20 | 3000.00 | 1566.666667 |
| KING | 10 | 5000.00 | 1566.666667 |
| FORD | 20 | 3000.00 | 1566.666667 |
------------------------------------- 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 emp.ename,emp.deptno,sal,maxsal from emp,(select deptno,max(sal) maxsal from emp group by deptno) tmp where emp.saltmp.maxsal;
---------------------------------
| ename | deptno | sal | maxsal |
---------------------------------
| BLAKE | 30 | 2850.00 | 2850.00 |
| SCOTT | 20 | 3000.00 | 3000.00 |
| KING | 10 | 5000.00 | 5000.00 |
| FORD | 20 | 3000.00 | 3000.00 |
---------------------------------
显示每个部门的信息部门名编号地址和人员数量
mysql select dept.dname,dept.deptno,dept.loc,count(*) from emp,dept where emp.deptnodept.deptno group by dept.dname,dept.deptno,dept.loc;
----------------------------------------
| dname | deptno | loc | count(*) |
----------------------------------------
| ACCOUNTING | 10 | NEW YORK | 3 |
| RESEARCH | 20 | DALLAS | 5 |
| SALES | 30 | CHICAGO | 6 |
----------------------------------------mysql select dept.dname,dept.deptno,dept.loc,tb1.人员数量 from dept,(select deptno,count(*) 人员数量 from emp group by deptno) tb1 where dept.deptnotb1.deptno;
--------------------------------------------
| dname | deptno | loc | 人员数量 |
--------------------------------------------
| ACCOUNTING | 10 | NEW YORK | 3 |
| RESEARCH | 20 | DALLAS | 5 |
| SALES | 30 | CHICAGO | 6 |
--------------------------------------------
6. 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。 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。
7. 表的内外连接
7.1 内连接
当我们使用多表查询时就是一种内连接这种内连接有种专门的写法
select * from tb_1 inner join tb_2 on 连接的条件 and 其他条件 我们要显示部门名员工名字薪水
mysql select dname,ename,sal from emp inner join dept on emp.deptnodept.deptno;
-----------------------------
| dname | ename | sal |
-----------------------------
| RESEARCH | SMITH | 800.00 |
| SALES | ALLEN | 1600.00 |
| SALES | WARD | 1250.00 |
| RESEARCH | JONES | 2975.00 |
| SALES | MARTIN | 1250.00 |
| SALES | BLAKE | 2850.00 |
| ACCOUNTING | CLARK | 2450.00 |
| RESEARCH | SCOTT | 3000.00 |
| ACCOUNTING | KING | 5000.00 |
| SALES | TURNER | 1500.00 |
| RESEARCH | ADAMS | 1100.00 |
| SALES | JAMES | 950.00 |
| RESEARCH | FORD | 3000.00 |
| ACCOUNTING | MILLER | 1300.00 |
-----------------------------
7.2 外连接 左外连接 右外连接
这种连接会根据条件匹配一方的条件如果是左外连接会将左边的表全部展现出来同理右外连接也是如此。
select * from tb_1 left join tb_2 on 连接条件 and 其他条件
我们创建一个学生表stu和一个成绩表cj具体的情况如下
mysql select * from stu;
--------------
| id | name |
--------------
| 1 | 小明 |
| 2 | 小红 |
| 3 | 小刚 |
| 4 | 小华 |
--------------
4 rows in set (0.00 sec)mysql select * from cj;
-------------
| id | score |
-------------
| 1 | 26 |
| 2 | 98 |
| 3 | 60 |
| 11 | 68 |
| 20 | 59 |
-------------
5 rows in set (0.00 sec)
1. 我们使用左外连接以id为连接条件右表会尽可能匹配左表左表会全部展出
mysql select * from stu left join cj on stu.idcj.id;
---------------------------
| id | name | id | score |
---------------------------
| 1 | 小明 | 1 | 26 |
| 2 | 小红 | 2 | 98 |
| 3 | 小刚 | 3 | 60 |
| 4 | 小华 | NULL | NULL |
---------------------------
2. 我们使用右外连接条件同上
mysql select * from stu right join cj on stu.idcj.id;
---------------------------
| id | name | id | score |
---------------------------
| 1 | 小明 | 1 | 26 |
| 2 | 小红 | 2 | 98 |
| 3 | 小刚 | 3 | 60 |
| NULL | NULL | 11 | 68 |
| NULL | NULL | 20 | 59 |
---------------------------
