MySQL数据库篇之单表查询
主要内容：
一、单表查询的语法
二、关键字的执行优先级
三、简单查询
四、where约束
五、分组查询 group by
六、having过滤
七、查询排序 order by
八、限制查询的记录数 limit
九、使用正则表达式查询
1️⃣ 单表查询的语法
SELECT 字段1,字段2... FROM 表名
WHERE 条件
GROUP BY field
HAVING 筛选
ORDER BY field
LIMIT 限制条数
2️⃣ 关键字的执行优先级
重点中的重点：关键字的执行优先级（从上至下）
from # 找到表
where # 拿着where指定的约束条件，去文件/表中取出一条条记录
group by # 将取出的一条条记录进行分组group by，如果没有group by，则整体作为一组
having # 将分组的结果进行having过滤
select # 执行select
distinct # 去重
order by # 将结果按条件排序
limit # 限制结果的显示条数
3️⃣ 简单查询
company.employee
员工id id int
姓名 emp_name varchar
性别 sex enum
年龄 age int
入职日期 hire_date date
岗位 post varchar
职位描述 post_comment varchar
薪水 salary double
办公室 office int
部门编号 depart_id int
1、创建表
create table employee(
id int not null unique auto_increment,
name varchar(20) not null,
sex enum('male','female') not null default 'male',
age int(3) unsigned not null default 28,
hire_date date not null,
post varchar(50),
post_comment varchar(100),
salary double(15,2),
office int,
depart_id int
);
2、查看表结构
mysql> desc employee;
+--------------+-----------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+-----------------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(20) | NO | | NULL | |
| sex | enum('male','female') | NO | | male | |
| age | int(3) unsigned | NO | | 28 | |
| hire_date | date | NO | | NULL | |
| post | varchar(50) | YES | | NULL | |
| post_comment | varchar(100) | YES | | NULL | |
| salary | double(15,2) | YES | | NULL | |
| office | int(11) | YES | | NULL | |
| depart_id | int(11) | YES | | NULL | |
+--------------+-----------------------+------+-----+---------+----------------+
3、插入记录
#三个部门：教学，销售，运营
insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
('egon','male',18,'20170301','老男孩驻沙河办事处外交大使',7300.33,401,1), #以下是教学部
('alex','male',78,'20150302','teacher',1000000.31,401,1),
('wupeiqi','male',81,'20130305','teacher',8300,401,1),
('yuanhao','male',73,'20140701','teacher',3500,401,1),
('liwenzhou','male',28,'20121101','teacher',2100,401,1),
('jingliyang','female',18,'20110211','teacher',9000,401,1),
('jinxin','male',18,'19000301','teacher',30000,401,1),
('成龙','male',48,'20101111','teacher',10000,401,1),
('歪歪','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门
('丫丫','female',38,'20101101','sale',2000.35,402,2),
('丁丁','female',18,'20110312','sale',1000.37,402,2),
('星星','female',18,'20160513','sale',3000.29,402,2),
('格格','female',28,'20170127','sale',4000.33,402,2),
('张野','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门
('程咬金','male',18,'19970312','operation',20000,403,3),
('程咬银','female',18,'20130311','operation',19000,403,3),
('程咬铜','male',18,'20150411','operation',18000,403,3),
('程咬铁','female',18,'20140512','operation',17000,403,3)
;
#ps：如果在windows系统中，插入中文字符，select的结果为空白，可以将所有字符编码统一设置成gbk
4、简单查询
SELECT id,name,sex,age,hire_date,post,post_comment,salary,office,depart_id
FROM employee; # 等同于 select * from employee;
结果如下：
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)
select name,salary from employee;
结果如下：
+------------+------------+
| name | salary |
+------------+------------+
| egon | 7300.33 |
| alex | 1000000.31 |
| wupeiqi | 8300.00 |
| yuanhao | 3500.00 |
| liwenzhou | 2100.00 |
| jingliyang | 9000.00 |
| jinxin | 30000.00 |
| 成龙 | 10000.00 |
| 歪歪 | 3000.13 |
| 丫丫 | 2000.35 |
| 丁丁 | 1000.37 |
| 星星 | 3000.29 |
| 格格 | 4000.33 |
| 张野 | 10000.13 |
| 程咬金 | 20000.00 |
| 程咬银 | 19000.00 |
| 程咬铜 | 18000.00 |
| 程咬铁 | 17000.00 |
+------------+------------+
18 rows in set (0.00 sec)
5、避免重复 DISTINCT
select distinct post from employee;
查询结果如下：
+-----------------------------------------+
| post |
+-----------------------------------------+
| 老男孩驻沙河办事处外交大使 |
| teacher |
| sale |
| operation |
+-----------------------------------------+
4 rows in set (0.00 sec)
6、通过四则运算查询
SELECT name, salary*12 FROM employee; # 计算年薪
SELECT name, salary*12 AS Annual_salary FROM employee; # 计算年薪并重命名为 Annual_salary
SELECT name, salary*12 Annual_salary FROM employee; # 计算年薪并重命名为 Annual_salary，省略as
查询结果如下：
+------------+---------------+
| name | Annual_salary |
+------------+---------------+
| egon | 87603.96 |
| alex | 12000003.72 |
| wupeiqi | 99600.00 |
| yuanhao | 42000.00 |
| liwenzhou | 25200.00 |
| jingliyang | 108000.00 |
| jinxin | 360000.00 |
| 成龙 | 120000.00 |
| 歪歪 | 36001.56 |
| 丫丫 | 24004.20 |
| 丁丁 | 12004.44 |
| 星星 | 36003.48 |
| 格格 | 48003.96 |
| 张野 | 120001.56 |
| 程咬金 | 240000.00 |
| 程咬银 | 228000.00 |
| 程咬铜 | 216000.00 |
| 程咬铁 | 204000.00 |
+------------+---------------+
18 rows in set (0.00 sec)
7、定义显示格式
CONCAT() 函数用于连接字符串
SELECT CONCAT('姓名: ',name,' 年薪: ', salary*12) AS Annual_salary
FROM employee;
+-----------------------------------------+
| Annual_salary |
+-----------------------------------------+
| 姓名：egon 年薪：87603.96 |
| 姓名：alex 年薪：12000003.72 |
| 姓名：wupeiqi 年薪：99600.00 |
| 姓名：yuanhao 年薪：42000.00 |
| 姓名：liwenzhou 年薪：25200.00 |
| 姓名：jingliyang 年薪：108000.00 |
| 姓名：jinxin 年薪：360000.00 |
| 姓名：成龙 年薪：120000.00 |
| 姓名：歪歪 年薪：36001.56 |
| 姓名：丫丫 年薪：24004.20 |
| 姓名：丁丁 年薪：12004.44 |
| 姓名：星星 年薪：36003.48 |
| 姓名：格格 年薪：48003.96 |
| 姓名：张野 年薪：120001.56 |
| 姓名：程咬金 年薪：240000.00 |
| 姓名：程咬银 年薪：228000.00 |
| 姓名：程咬铜 年薪：216000.00 |
| 姓名：程咬铁 年薪：204000.00 |
+-----------------------------------------+
18 rows in set (0.00 sec)
CONCAT_WS() 第一个参数为分隔符
SELECT CONCAT_WS(':',name,salary*12) AS Annual_salary
FROM employee;
+----------------------+
| Annual_salary |
+----------------------+
| egon:87603.96 |
| alex:12000003.72 |
| wupeiqi:99600.00 |
| yuanhao:42000.00 |
| liwenzhou:25200.00 |
| jingliyang:108000.00 |
| jinxin:360000.00 |
| 成龙:120000.00 |
| 歪歪:36001.56 |
| 丫丫:24004.20 |
| 丁丁:12004.44 |
| 星星:36003.48 |
| 格格:48003.96 |
| 张野:120001.56 |
| 程咬金:240000.00 |
| 程咬银:228000.00 |
| 程咬铜:216000.00 |
| 程咬铁:204000.00 |
+----------------------+
18 rows in set (0.00 sec)
练习题：
1、 查出所有员工的名字，薪资,格式为<名字:egon><薪资:3000>
2、查出所有的岗位（去掉重复）
3、查出所有员工名字，以及他们的年薪,年薪的字段名为annual_year
参考结果：
mysql> select concat('<','名字：',name,'>','<','薪资：','salary','>') from employee;
+---------------------------------------------------------------+
| concat('<','名字：',name,'>','<','薪资：','salary','>') |
+---------------------------------------------------------------+
| <名字：egon><薪资：salary> |
| <名字：alex><薪资：salary> |
| <名字：wupeiqi><薪资：salary> |
| <名字：yuanhao><薪资：salary> |
| <名字：liwenzhou><薪资：salary> |
| <名字：jingliyang><薪资：salary> |
| <名字：jinxin><薪资：salary> |
| <名字：成龙><薪资：salary> |
| <名字：歪歪><薪资：salary> |
| <名字：丫丫><薪资：salary> |
| <名字：丁丁><薪资：salary> |
| <名字：星星><薪资：salary> |
| <名字：格格><薪资：salary> |
| <名字：张野><薪资：salary> |
| <名字：程咬金><薪资：salary> |
| <名字：程咬银><薪资：salary> |
| <名字：程咬铜><薪资：salary> |
| <名字：程咬铁><薪资：salary> |
+---------------------------------------------------------------+
18 rows in set (0.00 sec)
mysql> select distinct depart_id from employee;
+-----------+
| depart_id |
+-----------+
| 1 |
| 2 |
| 3 |
+-----------+
3 rows in set (0.00 sec)
mysql> select name,salary*12 as annual_salary from employee;
+------------+---------------+
| name | annual_salary |
+------------+---------------+
| egon | 87603.96 |
| alex | 12000003.72 |
| wupeiqi | 99600.00 |
| yuanhao | 42000.00 |
| liwenzhou | 25200.00 |
| jingliyang | 108000.00 |
| jinxin | 360000.00 |
| 成龙 | 120000.00 |
| 歪歪 | 36001.56 |
| 丫丫 | 24004.20 |
| 丁丁 | 12004.44 |
| 星星 | 36003.48 |
| 格格 | 48003.96 |
| 张野 | 120001.56 |
| 程咬金 | 240000.00 |
| 程咬银 | 228000.00 |
| 程咬铜 | 216000.00 |
| 程咬铁 | 204000.00 |
+------------+---------------+
18 rows in set (0.00 sec)
4️⃣ WHERE约束
比较运算符：><>= <= <> !=
between 80 and 100 值在10到20之间
in(80,90,100) 值是10或20或30
like 'egon%'
pattern可以是%或_，
%表示任意多字符
_表示一个字符
逻辑运算符：在多个条件直接可以使用逻辑运算符 and or not
1、单条件查询
mysql> select name from employee where post = 'sale';
+--------+
| name |
+--------+
| 歪歪 |
| 丫丫 |
| 丁丁 |
| 星星 |
| 格格 |
+--------+
5 rows in set (0.00 sec)
2、多条件查询
SELECT name,salary FROM employee
WHERE post='teacher' AND salary>10000;
+--------+------------+
| name | salary |
+--------+------------+
| alex | 1000000.31 |
| jinxin | 30000.00 |
+--------+------------+
2 rows in set (0.00 sec)
3、关键字BETWEEN AND
SELECT name,salary FROM employee
WHERE salary BETWEEN 10000 AND 20000; # 所查数据在某一范围内
+-----------+----------+
| name | salary |
+-----------+----------+
| 成龙 | 10000.00 |
| 张野 | 10000.13 |
| 程咬金 | 20000.00 |
| 程咬银 | 19000.00 |
| 程咬铜 | 18000.00 |
| 程咬铁 | 17000.00 |
+-----------+----------+
6 rows in set (0.00 sec)
SELECT name,salary FROM employee
WHERE salary NOT BETWEEN 10000 AND 20000; # 所查数据不在某一范围内
+------------+------------+
| name | salary |
+------------+------------+
| egon | 7300.33 |
| alex | 1000000.31 |
| wupeiqi | 8300.00 |
| yuanhao | 3500.00 |
| liwenzhou | 2100.00 |
| jingliyang | 9000.00 |
| jinxin | 30000.00 |
| 歪歪 | 3000.13 |
| 丫丫 | 2000.35 |
| 丁丁 | 1000.37 |
| 星星 | 3000.29 |
| 格格 | 4000.33 |
+------------+------------+
12 rows in set (0.00 sec)
4、关键字 IS NULL（判断某个字段是否为NULL不能用等号，需要用 IS）
SELECT name,post_comment FROM employee
WHERE post_comment IS NULL;
+------------+--------------+
| name | post_comment |
+------------+--------------+
| egon | NULL |
| alex | NULL |
| wupeiqi | NULL |
| yuanhao | NULL |
| liwenzhou | NULL |
| jingliyang | NULL |
| jinxin | NULL |
| 成龙 | NULL |
| 歪歪 | NULL |
| 丫丫 | NULL |
| 丁丁 | NULL |
| 星星 | NULL |
| 格格 | NULL |
| 张野 | NULL |
| 程咬金 | NULL |
| 程咬银 | NULL |
| 程咬铜 | NULL |
| 程咬铁 | NULL |
+------------+--------------+
18 rows in set (0.00 sec)
SELECT name,post_comment FROM employee
WHERE post_comment IS NOT NULL;
Empty set (0.00 sec)
SELECT name,post_comment FROM employee
WHERE post_comment=''; 注意''是空字符串，不是null
Empty set (0.00 sec)
执行
update employee set post_comment='' where id=2;
再用上条查看效果
mysql> update employee set post_comment='' where id=2;
Query OK, 1 row affected (0.06 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> SELECT name,post_comment FROM employee
-> WHERE post_comment='';
+------+--------------+
| name | post_comment |
+------+--------------+
| alex | |
+------+--------------+
1 row in set (0.00 sec)
5、关键字 IN 集合查询
SELECT name,salary FROM employee
WHERE salary=3000 OR salary=3500 OR salary=4000 OR salary=9000 ;
SELECT name,salary FROM employee
WHERE salary IN (3000,3500,4000,9000) ;
上面两条语句的查询结果完全相同：
+------------+---------+
| name | salary |
+------------+---------+
| yuanhao | 3500.00 |
| jingliyang | 9000.00 |
+------------+---------+
2 rows in set (0.00 sec)
SELECT name,salary FROM employee
WHERE salary NOT IN (3000,3500,4000,9000) ; # 查询不在某一集合的范围内的数据
+-----------+------------+
| name | salary |
+-----------+------------+
| egon | 7300.33 |
| alex | 1000000.31 |
| wupeiqi | 8300.00 |
| liwenzhou | 2100.00 |
| jinxin | 30000.00 |
| 成龙 | 10000.00 |
| 歪歪 | 3000.13 |
| 丫丫 | 2000.35 |
| 丁丁 | 1000.37 |
| 星星 | 3000.29 |
| 格格 | 4000.33 |
| 张野 | 10000.13 |
| 程咬金 | 20000.00 |
| 程咬银 | 19000.00 |
| 程咬铜 | 18000.00 |
| 程咬铁 | 17000.00 |
+-----------+------------+
16 rows in set (0.00 sec)
6、关键字 LIKE 模糊查询
通配符’%’ # 匹配多个字符
SELECT * FROM employee
WHERE name LIKE 'eg%';
通配符’_’ # 每个匹配一字符
SELECT * FROM employee
WHERE name LIKE 'al__';
练习题：
1. 查看岗位是teacher的员工姓名、年龄
2. 查看岗位是teacher且年龄大于30岁的员工姓名、年龄
3. 查看岗位是teacher且薪资在9000-1000范围内的员工姓名、年龄、薪资
4. 查看岗位描述不为NULL的员工信息
5. 查看岗位是teacher且薪资是10000或9000或30000的员工姓名、年龄、薪资
6. 查看岗位是teacher且薪资不是10000或9000或30000的员工姓名、年龄、薪资
7. 查看岗位是teacher且名字是jin开头的员工姓名、年薪
select name,age from employee where post = 'teacher';
select name,age from employee where post='teacher' and age > 30;
select name,age,salary from employee where post='teacher' and salary between 9000 and 10000;
select * from employee where post_comment is not null;
select name,age,salary from employee where post='teacher' and salary in (10000,9000,30000);
select name,age,salary from employee where post='teacher' and salary not in (10000,9000,30000);
select name,salary*12 from employee where post='teacher' and name like 'jin%';
5️⃣ 分组查询：GROUP BY
1、什么是分组？为什么要分组？
①首先必须明确，分组发生在where之后，即分组是基于where之后得到的记录而进行的。
②分组指的是：将所有记录按照某个相同字段进行归类，比如针对员工信息表的职位分组，或者按照性别进行分组等。
③为何要分组呢？
如取每个部门的最高工资；取每个部门的员工数；取男人数和女人数等...
小窍门：“每”这个字后面的字段，就是我们分组的依据。
④前提：
可以按照任意字段分组，但是分组完毕后，比如group by post，只能查看post字段，
如果想查看组内信息，需要借助聚合函数。
2、ONLY_FULL_GROUP_BY
mysql> set global sql_mode='ONLY_FULL_GROUP_BY';
Query OK, 0 rows affected (0.00 sec)
mysql> select * from employee group by post;
ERROR 1055 (42000): 'single.employee.id' isn't in GROUP BY
mysql> select post,count(id) from employee group by post; #只能查看分组依据和使用聚合函数
+-----------------------------------------+-----------+
| post | count(id) |
+-----------------------------------------+-----------+
| operation | 5 |
| sale | 5 |
| teacher | 7 |
| 老男孩驻沙河办事处外交大使 | 1 |
+-----------------------------------------+-----------+
4 rows in set (0.00 sec)
3、GROUP BY
# 单独使用GROUP BY关键字分组
mysql> SELECT post FROM employee GROUP BY post;
+-----------------------------------------+
| post |
+-----------------------------------------+
| operation |
| sale |
| teacher |
| 老男孩驻沙河办事处外交大使 |
+-----------------------------------------+
4 rows in set (0.00 sec)
# GROUP BY关键字和GROUP_CONCAT()函数一起使用(下面两式查询结果相同，第二个表达式多了个重命名的过程)
SELECT post,GROUP_CONCAT(name) FROM employee GROUP BY post;#按照岗位分组，并查看组内成员名
SELECT post,GROUP_CONCAT(name) as emp_members FROM employee GROUP BY post;
效果如下：
mysql> SELECT post,GROUP_CONCAT(name) FROM employee GROUP BY post;
+-----------------------------------------+---------------------------------------------------------+
| post | GROUP_CONCAT(name) |
+-----------------------------------------+---------------------------------------------------------+
| operation | 程咬铁,程咬铜,程咬银,程咬金,张野 |
| sale | 格格,星星,丁丁,丫丫,歪歪 |
| teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex |
| 老男孩驻沙河办事处外交大使 | egon |
+-----------------------------------------+---------------------------------------------------------+
4 rows in set (0.00 sec)
mysql> SELECT post,GROUP_CONCAT(name) as emp_members FROM employee GROUP BY post;
+-----------------------------------------+---------------------------------------------------------+
| post | emp_members |
+-----------------------------------------+---------------------------------------------------------+
| operation | 程咬铁,程咬铜,程咬银,程咬金,张野 |
| sale | 格格,星星,丁丁,丫丫,歪歪 |
| teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex |
| 老男孩驻沙河办事处外交大使 | egon |
+-----------------------------------------+---------------------------------------------------------+
4 rows in set (0.00 sec)
# GROUP BY与聚合函数一起使用
select post,count(id) as count from employee group by post;#按照岗位分组，并查看每个组有多少
mysql> select post,count(id) as count from employee group by post;
+-----------------------------------------+-------+
| post | count |
+-----------------------------------------+-------+
| operation | 5 |
| sale | 5 |
| teacher | 7 |
| 老男孩驻沙河办事处外交大使 | 1 |
+-----------------------------------------+-------+
4 rows in set (0.00 sec)
注意：
如果我们用unique的字段作为分组的依据，则每一条记录自成一组，这种分组没有意义
多条记录之间的某个字段值相同，该字段通常用来作为分组的依据
4、聚合函数
#强调：聚合函数聚合的是组的内容，若是没有分组，则默认一组
常用的实例：
SELECT COUNT(*) FROM employee;
mysql> SELECT COUNT(*) FROM employee;
+----------+
| COUNT(*) |
+----------+
| 18 |
+----------+
1 row in set (0.00 sec)
SELECT COUNT(*) FROM employee WHERE depart_id=1;
mysql> SELECT COUNT(*) FROM employee WHERE depart_id=1;
+----------+
| COUNT(*) |
+----------+
| 8 |
+----------+
1 row in set (0.00 sec)
SELECT MAX(salary) FROM employee;
mysql> SELECT MAX(salary) FROM employee;
+-------------+
| MAX(salary) |
+-------------+
| 1000000.31 |
+-------------+
1 row in set (0.00 sec)
SELECT MIN(salary) FROM employee;
mysql> SELECT MIN(salary) FROM employee;
+-------------+
| MIN(salary) |
+-------------+
| 1000.37 |
+-------------+
1 row in set (0.00 sec)
SELECT AVG(salary) FROM employee;
mysql> SELECT AVG(salary) FROM employee;
+--------------+
| AVG(salary) |
+--------------+
| 64844.568889 |
+--------------+
1 row in set (0.00 sec)
SELECT SUM(salary) FROM employee;
mysql> SELECT SUM(salary) FROM employee;
+-------------+
| SUM(salary) |
+-------------+
| 1167202.24 |
+-------------+
1 row in set (0.00 sec)
SELECT SUM(salary) FROM employee WHERE depart_id=3;
mysql> SELECT SUM(salary) FROM employee WHERE depart_id=3;
+-------------+
| SUM(salary) |
+-------------+
| 84000.13 |
+-------------+
1 row in set (0.00 sec)
5、小练习
1. 查询岗位名以及岗位包含的所有员工名字
2. 查询岗位名以及各岗位内包含的员工个数
3. 查询公司内男员工和女员工的个数
4. 查询岗位名以及各岗位的平均薪资
5. 查询岗位名以及各岗位的最高薪资
6. 查询岗位名以及各岗位的最低薪资
7. 查询男员工与男员工的平均薪资，女员工与女员工的平均薪资
题目一：
mysql> select post,group_concat(name) from employee group by post;
+-----------------------------------------+---------------------------------------------------------+
| post | group_concat(name) |
+-----------------------------------------+---------------------------------------------------------+
| operation | 程咬铁,程咬铜,程咬银,程咬金,张野 |
| sale | 格格,星星,丁丁,丫丫,歪歪 |
| teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex |
| 老男孩驻沙河办事处外交大使 | egon |
+-----------------------------------------+---------------------------------------------------------+
4 rows in set (0.00 sec)
题目二：
mysql> select post,count(id) as count_emp from employee group by post;
+-----------------------------------------+-----------+
| post | count_emp |
+-----------------------------------------+-----------+
| operation | 5 |
| sale | 5 |
| teacher | 7 |
| 老男孩驻沙河办事处外交大使 | 1 |
+-----------------------------------------+-----------+
4 rows in set (0.00 sec)
题目三：
mysql> select sex,count(id) as count_emp from employee group by sex;
+--------+-----------+
| sex | count_emp |
+--------+-----------+
| male | 10 |
| female | 8 |
+--------+-----------+
2 rows in set (0.00 sec)
题目四：
mysql> select post,avg(salary) as avg_salary from employee group by post;
+-----------------------------------------+---------------+
| post | avg_salary |
+-----------------------------------------+---------------+
| operation | 16800.026000 |
| sale | 2600.294000 |
| teacher | 151842.901429 |
| 老男孩驻沙河办事处外交大使 | 7300.330000 |
+-----------------------------------------+---------------+
4 rows in set (0.00 sec)
题目五：
mysql> select post,max(salary) as max_salary from employee group by post;
+-----------------------------------------+------------+
| post | max_salary |
+-----------------------------------------+------------+
| operation | 20000.00 |
| sale | 4000.33 |
| teacher | 1000000.31 |
| 老男孩驻沙河办事处外交大使 | 7300.33 |
+-----------------------------------------+------------+
4 rows in set (0.00 sec)
题目六：
mysql> select post,min(salary) as min_salary from employee group by post;
+-----------------------------------------+------------+
| post | min_salary |
+-----------------------------------------+------------+
| operation | 10000.13 |
| sale | 1000.37 |
| teacher | 2100.00 |
| 老男孩驻沙河办事处外交大使 | 7300.33 |
+-----------------------------------------+------------+
4 rows in set (0.00 sec)
题目七：
mysql> select sex,avg(salary) avg_salary from employee group by sex;
+--------+---------------+
| sex | avg_salary |
+--------+---------------+
| male | 110920.077000 |
| female | 7250.183750 |
+--------+---------------+
2 rows in set (0.00 sec)
6️⃣ HAVING过滤
1、HAVING与WHERE的区别：
#执行优先级从高到低：where > group by > having
#1. Where 发生在分组group by之前，因而Where中可以有任意字段，但是绝对不能使用聚合函数。
#2. Having发生在分组group by之后，因而Having中可以使用分组的字段，无法直接取到其他字段,可以使用聚合函
2、实例对比：
mysql> select * from emp where salary > 100000;
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
row in set (0.00 sec)
mysql> select * from emp having salary > 100000;
ERROR 1463 (42000): Non-grouping field 'salary' is used in HAVING clause
mysql> select post,group_concat(name) from emp group by post having avg(salary) > 10000;
+-----------+-------------------------------------------------------+
| post | group_concat(name) |
+-----------+-------------------------------------------------------+
| operation | 程咬铁,程咬铜,程咬银,程咬金,张野 |
| teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex |
+-----------+-------------------------------------------------------+
rows in set (0.00 sec)
小练习
1. 查询各岗位内包含的员工个数小于2的岗位名、岗位内包含员工名字、个数
3. 查询各岗位平均薪资大于10000的岗位名、平均工资
4. 查询各岗位平均薪资大于10000且小于20000的岗位名、平均工资
题目1：
mysql> select post,group_concat(name),count(id) as count_emp from employee group by post;
+-----------------------------------------+---------------------------------------------------------+-----------+
| post | group_concat(name) | count_emp |
+-----------------------------------------+---------------------------------------------------------+-----------+
| operation | 程咬铁,程咬铜,程咬银,程咬金,张野 | 5 |
| sale | 格格,星星,丁丁,丫丫,歪歪 | 5 |
| teacher | 成龙,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex | 7 |
| 老男孩驻沙河办事处外交大使 | egon | 1 |
+-----------------------------------------+---------------------------------------------------------+-----------+
4 rows in set (0.00 sec)
题目2：
mysql> select post,avg(salary) as avg_salary from employee group by post having avg(salary)>10000;
+-----------+---------------+
| post | avg_salary |
+-----------+---------------+
| operation | 16800.026000 |
| teacher | 151842.901429 |
+-----------+---------------+
2 rows in set (0.00 sec)
题目3：
mysql> select post,avg(salary) as avg_salary from employee group by post having avg(salary)>10000 and avg(salary)<20000;
+-----------+--------------+
| post | avg_salary |
+-----------+--------------+
| operation | 16800.026000 |
+-----------+--------------+
1 row in set (0.00 sec)
7️⃣ 查询排序：ORDER BY
1、按单列排序
比较以下几种方式
SELECT * FROM employee ORDER BY salary;
SELECT * FROM employee ORDER BY salary ASC;
SELECT * FROM employee ORDER BY salary DESC;
对比效果如下：
mysql> SELECT * FROM employee ORDER BY salary;
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
| 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)
mysql> SELECT * FROM employee ORDER BY salary ASC;
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
| 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)
mysql> SELECT * FROM employee ORDER BY salary DESC;
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
| 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)
2、按多列排序：先按照age排序，如果年纪相同，则按照薪资排序
SELECT * from employee
ORDER BY age,
salary DESC;
小练习
1. 查询所有员工信息，先按照age升序排序，如果age相同则按照hire_date降序排序
2. 查询各岗位平均薪资大于10000的岗位名、平均工资,结果按平均薪资升序排列
3. 查询各岗位平均薪资大于10000的岗位名、平均工资,结果按平均薪资降序排列
题目1：
mysql> select * from employee order by age asc , hire_date desc;
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
18 rows in set (0.00 sec)
题目2：
l> select post,avg(salary) as avg_salary from employee group by post having avg(salary)>10000 order by avg_salary asc;
+-----------+---------------+
| post | avg_salary |
+-----------+---------------+
| operation | 16800.026000 |
| teacher | 151842.901429 |
+-----------+---------------+
2 rows in set (0.00 sec)
题目3：
mysql> select post,avg(salary) as avg_salary from employee group by post having avg(salary)>10000 order by avg_salary desc;
+-----------+---------------+
| post | avg_salary |
+-----------+---------------+
| teacher | 151842.901429 |
| operation | 16800.026000 |
+-----------+---------------+
2 rows in set (0.00 sec)
8️⃣ 限制查询的记录数：LIMIT
示例：
SELECT * FROM employee ORDER BY salary DESC
LIMIT 3; #默认初始位置为0
SELECT * FROM employee ORDER BY salary DESC
LIMIT 0,5; #从第0开始，即先查询出第一条，然后包含这一条在内往后查5条
SELECT * FROM employee ORDER BY salary DESC
LIMIT 5,5; #从第5开始，即先查询出第6条，然后包含这一条在内往后查5条
小练习：将employee表中的数据分页显示，每页6条数据。
效果如下：
mysql> select * from employee limit 0,6;
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
+----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+
6 rows in set (0.00 sec)
mysql> select * from employee limit 6,6;
+----+--------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+--------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | 成龙 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
+----+--------+--------+-----+------------+---------+--------------+----------+--------+-----------+
6 rows in set (0.00 sec)
mysql> select * from employee limit 12,6;
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 |
| 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 16 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 17 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 18 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
6 rows in set (0.00 sec)
9️⃣ 使用正则表达式查询
常用的语法如下：
SELECT * FROM employee WHERE name REGEXP '^ale';
SELECT * FROM employee WHERE name REGEXP 'on$';
SELECT * FROM employee WHERE name REGEXP 'm{2}';
示例：
mysql> select * from employee where name regexp '^ale';
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
1 row in set (0.00 sec)
mysql> SELECT * FROM employee WHERE name REGEXP 'on$';
+----+------+------+-----+------------+-----------------------------------------+--------------+---------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+-----------------------------------------+--------------+---------+--------+-----------+
| 1 | egon | male | 18 | 2017-03-01 | 老男孩驻沙河办事处外交大使 | NULL | 7300.33 | 401 | 1 |
+----+------+------+-----+------------+-----------------------------------------+--------------+---------+--------+-----------+
1 row in set (0.00 sec)
mysql> SELECT * FROM employee WHERE name REGEXP 'm{2}';
Empty set (0.00 sec)
mysql> SELECT * FROM employee WHERE name like 'yuan%';
+----+---------+------+-----+------------+---------+--------------+---------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+---------+------+-----+------------+---------+--------------+---------+--------+-----------+
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
+----+---------+------+-----+------------+---------+--------------+---------+--------+-----------+
1 row in set (0.00 sec)
mysql> SELECT * FROM employee WHERE name regexp 'hao$';
+----+---------+------+-----+------------+---------+--------------+---------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+---------+------+-----+------------+---------+--------------+---------+--------+-----------+
| 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
+----+---------+------+-----+------------+---------+--------------+---------+--------+-----------+
1 row in set (0.00 sec)
小练习
查看所有员工中名字是jin开头，n或者g结果的员工信息
mysql> select * from employee where name regexp '^jin.*[gn]$';
+----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 |
| 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
+----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+
2 rows in set (0.00 sec)
读书原为修身，正己才能正人正世；不修身不正己而去正人正世者，无一不是盗名欺世；你把念过的书能用上十之一二，就是很了不得的人了。——朱先生
