时间:2021-07-01 10:21:17 帮助过:13人阅读
- <span style="color: #000000">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</span>
- <span style="color: #000000">重点中的重点:关键字的执行优先级
- </span>1、<span style="color: #0000ff">from</span><span style="color: #000000"> 先找表
- </span>2<span style="color: #000000">、where 拿着约束条件做筛选
- </span>3<span style="color: #000000">、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
- </span>4<span style="color: #000000">、having 将分组结果进行过滤
- </span>5<span style="color: #000000">、select 执行select
- </span>6<span style="color: #000000">、distinct 去重
- </span>7<span style="color: #000000">、order by 将结果排序
- </span>8、limit 限制显示条数
准备表
- <span style="color: #000000">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
- </span><span style="color: #008000">#</span><span style="color: #008000">创建表</span>
- <span style="color: #000000">create table employee(
- id int </span><span style="color: #0000ff">not</span><span style="color: #000000"> null unique auto_increment,
- name varchar(</span>20) <span style="color: #0000ff">not</span><span style="color: #000000"> null,
- sex enum(</span><span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>) <span style="color: #0000ff">not</span> null default <span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>, <span style="color: #008000">#</span><span style="color: #008000">大部分是男的</span>
- age int(3) unsigned <span style="color: #0000ff">not</span> null default 28<span style="color: #000000">,
- hire_date date </span><span style="color: #0000ff">not</span><span style="color: #000000"> null,
- post varchar(</span>50<span style="color: #000000">),
- post_comment varchar(</span>100<span style="color: #000000">),
- salary double(</span>15,2<span style="color: #000000">),
- office int, </span><span style="color: #008000">#</span><span style="color: #008000">一个部门一个屋子</span>
- <span style="color: #000000">depart_id int
- );
- </span><span style="color: #008000">#</span><span style="color: #008000">查看表结构</span>
- mysql><span style="color: #000000"> desc employee;
- </span>+--------------+-----------------------+------+-----+---------+----------------+
- | Field | Type | Null | Key | Default | Extra |
- +--------------+-----------------------+------+-----+---------+----------------+
- | id | int(11) | NO | PRI | NULL | auto_increment |
- | name | varchar(20) | NO | | NULL | |
- | sex | enum(<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>) | 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 | |
- +--------------+-----------------------+------+-----+---------+----------------+
- <span style="color: #008000">#</span><span style="color: #008000">插入记录</span><span style="color: #008000">
- #</span><span style="color: #008000">三个部门:教学,销售,运营</span>
- <span style="color: #000000">insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values
- (</span><span style="color: #800000">‘</span><span style="color: #800000">egon</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20170301</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">老男孩驻沙河办事处外交大使</span><span style="color: #800000">‘</span>,7300.33,401,1), <span style="color: #008000">#</span><span style="color: #008000">以下是教学部</span>
- (<span style="color: #800000">‘</span><span style="color: #800000">alex</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,78,<span style="color: #800000">‘</span><span style="color: #800000">20150302</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,1000000.31,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">wupeiqi</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,81,<span style="color: #800000">‘</span><span style="color: #800000">20130305</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,8300,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">yuanhao</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,73,<span style="color: #800000">‘</span><span style="color: #800000">20140701</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,3500,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">liwenzhou</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,28,<span style="color: #800000">‘</span><span style="color: #800000">20121101</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,2100,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">jingliyang</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20110211</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,9000,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">jinxin</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">19000301</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,30000,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">成龙</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,48,<span style="color: #800000">‘</span><span style="color: #800000">20101111</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span>,10000,401,1<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">歪歪</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,48,<span style="color: #800000">‘</span><span style="color: #800000">20150311</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">sale</span><span style="color: #800000">‘</span>,3000.13,402,2),<span style="color: #008000">#</span><span style="color: #008000">以下是销售部门</span>
- (<span style="color: #800000">‘</span><span style="color: #800000">丫丫</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,38,<span style="color: #800000">‘</span><span style="color: #800000">20101101</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">sale</span><span style="color: #800000">‘</span>,2000.35,402,2<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">丁丁</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20110312</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">sale</span><span style="color: #800000">‘</span>,1000.37,402,2<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">星星</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20160513</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">sale</span><span style="color: #800000">‘</span>,3000.29,402,2<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">格格</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,28,<span style="color: #800000">‘</span><span style="color: #800000">20170127</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">sale</span><span style="color: #800000">‘</span>,4000.33,402,2<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">张野</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,28,<span style="color: #800000">‘</span><span style="color: #800000">20160311</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">operation</span><span style="color: #800000">‘</span>,10000.13,403,3), <span style="color: #008000">#</span><span style="color: #008000">以下是运营部门</span>
- (<span style="color: #800000">‘</span><span style="color: #800000">程咬金</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">19970312</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">operation</span><span style="color: #800000">‘</span>,20000,403,3<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">程咬银</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20130311</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">operation</span><span style="color: #800000">‘</span>,19000,403,3<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">程咬铜</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">male</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20150411</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">operation</span><span style="color: #800000">‘</span>,18000,403,3<span style="color: #000000">),
- (</span><span style="color: #800000">‘</span><span style="color: #800000">程咬铁</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">female</span><span style="color: #800000">‘</span>,18,<span style="color: #800000">‘</span><span style="color: #800000">20140512</span><span style="color: #800000">‘</span>,<span style="color: #800000">‘</span><span style="color: #800000">operation</span><span style="color: #800000">‘</span>,17000,403,3<span style="color: #000000">)
- ;
- </span><span style="color: #008000">#</span><span style="color: #008000">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</span>
- <span style="color: #000000">CONCAT() 函数用于连接字符串
- SELECT CONCAT(</span><span style="color: #800000">‘</span><span style="color: #800000">姓名: </span><span style="color: #800000">‘</span>,name,<span style="color: #800000">‘</span><span style="color: #800000"> 年薪: </span><span style="color: #800000">‘</span>, salary*12<span style="color: #000000">) <br>AS Annual_salary FROM employee;
- CONCAT_WS() 第一个参数为分隔符
- SELECT CONCAT_WS(</span><span style="color: #800000">‘</span><span style="color: #800000">:</span><span style="color: #800000">‘</span>,name,salary*12) AS Annual_salary FROM employee;
高级版
- select concat(<span style="color: #800000">‘</span><span style="color: #800000">naem:</span><span style="color: #800000">‘</span>,name) as name,concat(<span style="color: #800000">‘</span><span style="color: #800000">annual_salary:</span><span style="color: #800000">‘</span>,salary*12)<br> as annual_salary <span style="color: #0000ff">from</span> emp2;
2、
- 普通版: <br>select id,concat(name,‘:‘,sex,‘:‘,salary) as info from emp2;
- <span style="color: #008000">#</span><span style="color: #008000"> 进化版</span>
- select id,concat_ws(<span style="color: #800000">‘</span><span style="color: #800000">:</span><span style="color: #800000">‘</span>,name,sex,salary) as info <span style="color: #0000ff">from</span> emp2;
2、distinct 去重
as显示效果的区别:
3、where约束
- <span style="color: #000000">where字句中可以使用:
- </span>1. 比较运算符:> < >= <= <> !=
- 2. between 80 <span style="color: #0000ff">and</span> 100<span style="color: #000000"> 值在80到100之间,包括80和100
- </span>3. <span style="color: #0000ff">in</span>(80,90,100<span style="color: #000000">) 值是80或90或100
- </span>4. like <span style="color: #800000">‘</span><span style="color: #800000">egon%</span><span style="color: #800000">‘</span><span style="color: #000000">
- pattern可以是</span>%<span style="color: #000000">或_,
- </span>%<span style="color: #000000">表示任意多字符
- _表示任意一个字符
- </span>5. 逻辑运算符:在多个条件直接可以使用逻辑运算符 <span style="color: #0000ff">and</span> <span style="color: #0000ff">or</span> <span style="color: #0000ff">not</span>
- <span style="color: #008000">#</span><span style="color: #008000">1:单条件查询</span>
- <span style="color: #000000"> SELECT name FROM employee
- WHERE post</span>=<span style="color: #800000">‘</span><span style="color: #800000">sale</span><span style="color: #800000">‘</span><span style="color: #000000">;
- </span><span style="color: #008000">#</span><span style="color: #008000">2:多条件查询</span>
- <span style="color: #000000"> SELECT name,salary FROM employee
- WHERE post</span>=<span style="color: #800000">‘</span><span style="color: #800000">teacher</span><span style="color: #800000">‘</span> AND salary>10000<span style="color: #000000">;
- </span><span style="color: #008000">#</span><span style="color: #008000">3:关键字BETWEEN AND</span>
- <span style="color: #000000"> SELECT name,salary FROM employee
- WHERE salary BETWEEN </span>10000 AND 20000<span style="color: #000000">;
- SELECT name,salary FROM employee
- WHERE salary NOT BETWEEN </span>10000 AND 20000<span style="color: #000000">;
- </span><span style="color: #008000">#</span><span style="color: #008000">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)</span>
- <span style="color: #000000"> SELECT name,post_comment FROM employee
- WHERE post_comment IS NULL;
- SELECT name,post_comment FROM employee
- WHERE post_comment IS NOT NULL;
- SELECT name,post_comment FROM employee
- WHERE post_comment</span>=<span style="color: #800000">‘‘</span>; 注意<span style="color: #800000">‘‘</span><span style="color: #000000">是空字符串,不是null
- ps:
- 执行
- update employee set post_comment</span>=<span style="color: #800000">‘‘</span> where id=2<span style="color: #000000">;
- 再用上条查看,就会有结果了
- </span><span style="color: #008000">#</span><span style="color: #008000">5:关键字IN集合查询</span>
- <span style="color: #000000"> SELECT name,salary FROM employee
- WHERE salary</span>=3000 OR salary=3500 OR salary=4000 OR salary=9000<span style="color: #000000"> ;
- SELECT name,salary FROM employee
- WHERE salary IN (</span>3000,3500,4000,9000<span style="color: #000000">) ;
- SELECT name,salary FROM employee
- WHERE salary NOT IN (</span>3000,3500,4000,9000<span style="color: #000000">) ;
- </span><span style="color: #008000">#</span><span style="color: #008000">6:关键字LIKE模糊查询</span>
- 通配符’%<span style="color: #000000">’
- SELECT </span>*<span style="color: #000000"> FROM employee
- WHERE name LIKE </span><span style="color: #800000">‘</span><span style="color: #800000">eg%</span><span style="color: #800000">‘</span><span style="color: #000000">;
- 通配符’_’
- SELECT </span>*<span style="color: #000000"> FROM employee
- WHERE name LIKE </span><span style="color: #800000">‘</span><span style="color: #800000">al__</span><span style="color: #800000">‘</span>;
4、分组 group by
注意:使用分组只能查看分组的依据和聚合函数,若是查看其它信息,则默认是该组的第一条信息,这其实是没有意义的。如下:
- <span style="color: #008000">#</span><span style="color: #008000">1、首先明确一点: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</span>
- <span style="color: #008000">#</span><span style="color: #008000">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,<br>或者按照性别进行分组等</span>
- <span style="color: #008000">#</span><span style="color: #008000">3、为何要分组呢?</span>
- <span style="color: #000000"> 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
- 小窍门:‘每’这个字后面的字段,就是我们分组的依据
- </span><span style="color: #008000">#</span><span style="color: #008000">4、大前提:</span>
- 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,<br>如果想查看组内信息,需要借助于聚合函数
二 ONLY_FULL_GROUP_BY
- <span style="color: #008000">#</span><span style="color: #008000">查看MySQL 5.7默认的sql_mode如下:</span>
- mysql> select @@<span style="color: #0000ff">global</span><span style="color: #000000">.sql_mode;
- ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION
- </span><span style="color: #008000">#</span><span style="color: #008000">!!!注意</span>
- <span style="color: #000000">ONLY_FULL_GROUP_BY的语义就是确定select target list中的所有列的值都是明确语义,简单的说来,在ONLY_FULL_GROUP_BY模式下,target list中的值要么是来自于聚集函数的结果,<br>要么是来自于group by list中的表达式的值。
- </span><span style="color: #008000">#</span><span style="color: #008000">设置sql_mole如下操作(我们可以去掉ONLY_FULL_GROUP_BY模式):</span>
- mysql> set <span style="color: #0000ff">global</span> sql_mode=<span style="color: #800000">‘</span><span style="color: #800000">STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,<br>NO_ENGINE_SUBSTITUTION</span><span style="color: #800000">‘</span>;
三 GROUP BY
- <span style="color: #008000">#</span><span style="color: #008000"> 单独使用GROUP BY关键字分组</span>
- <span style="color: #000000"> SELECT post FROM employee GROUP BY post;
- 注意:我们按照post字段分组,那么select查询的字段只能是post,想要获取组内的其他相关信息,需要借助函数
- GROUP BY关键字和GROUP_CONCAT()函数一起使用
- SELECT post,GROUP_CONCAT(name) FROM employee GROUP BY post;<br></span><span style="color: #008000">#</span><span style="color: #008000">按照岗位分组,并查看组内成员名</span>
- <span style="color: #000000"> SELECT post,GROUP_CONCAT(name) as emp_members FROM employee GROUP BY post;
- </span><span style="color: #008000">GROUP BY与聚合函数一起使用</span>
- select post,count(id) as count <span style="color: #0000ff">from</span> employee group by post;<br><span style="color: #008000">#</span><span style="color: #008000">按照岗位分组,并查看每个组有多少人</span>
强调:
- <span style="color: #000000">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</span>
四 聚合函数
- <span style="color: #008000">#</span><span style="color: #008000">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</span>
- <span style="color: #000000">示例:
- SELECT COUNT(</span>*<span style="color: #000000">) FROM employee;
- SELECT COUNT(</span>*) FROM employee WHERE depart_id=1<span style="color: #000000">;
- SELECT MAX(salary) FROM employee;
- SELECT MIN(salary) FROM employee;
- SELECT AVG(salary) FROM employee;
- SELECT SUM(salary) FROM employee;
- SELECT SUM(salary) FROM employee WHERE depart_id</span>=3;
HAVING与WHERE不一样的地方在于!!!!!!
- <span style="color: #008000">#</span><span style="color: #008000">!!!执行优先级从高到低:where > group by > having </span><span style="color: #008000">
- #</span><span style="color: #008000">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。</span>
- <span style="color: #008000">#</span><span style="color: #008000">2. Having发生在分组group by之后,因而Having中可以使用分组的字段,<br>无法直接取到其他字段,可以使用聚合函数</span>
- <span style="color: #000000">按单列排序
- SELECT </span>*<span style="color: #000000"> FROM employee ORDER BY salary;
- SELECT </span>*<span style="color: #000000"> FROM employee ORDER BY salary ASC;
- SELECT </span>*<span style="color: #000000"> FROM employee ORDER BY salary DESC;
- 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 </span>* <span style="color: #0000ff">from</span><span style="color: #000000"> employee
- ORDER BY age,
- salary DESC;</span>
- <span style="color: #000000">示例:
- SELECT </span>*<span style="color: #000000"> FROM employee ORDER BY salary DESC
- LIMIT </span>3; <span style="color: #008000">#</span><span style="color: #008000">默认初始位置为0 </span>
- <span style="color: #000000">
- SELECT </span>*<span style="color: #000000"> FROM employee ORDER BY salary DESC
- LIMIT 0,</span>5; <span style="color: #008000">#</span><span style="color: #008000">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</span>
- <span style="color: #000000">
- SELECT </span>*<span style="color: #000000"> FROM employee ORDER BY salary DESC
- LIMIT </span>5,5; <span style="color: #008000">#</span><span style="color: #008000">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</span>
View Code
- SELECT * FROM employee WHERE name REGEXP <span style="color: #800000">‘</span><span style="color: #800000">^ale</span><span style="color: #800000">‘</span><span style="color: #000000">;
- SELECT </span>* FROM employee WHERE name REGEXP <span style="color: #800000">‘</span><span style="color: #800000">on$</span><span style="color: #800000">‘</span><span style="color: #000000">;
- SELECT </span>* FROM employee WHERE name REGEXP <span style="color: #800000">‘</span><span style="color: #800000">m{2}</span><span style="color: #800000">‘</span><span style="color: #000000">;
- 小结:对字符串匹配的方式
- WHERE name </span>= <span style="color: #800000">‘</span><span style="color: #800000">egon</span><span style="color: #800000">‘</span><span style="color: #000000">;
- WHERE name LIKE </span><span style="color: #800000">‘</span><span style="color: #800000">yua%</span><span style="color: #800000">‘</span><span style="color: #000000">;
- WHERE name REGEXP </span><span style="color: #800000">‘</span><span style="color: #800000">on$</span><span style="color: #800000">‘</span>;
mysql 单表查询
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