单表查询的语法
不带关键字的语法
select {1.*|2.字段名|3.四则运行|4.聚合函数} from 表名 [where 条件]
1.* 表示查询所有字段
2.可以手动要查询的字段
3.字段的值可以进行加减乘除运算
4.聚合函数,用于统计
where 是可选的
field()函数
可以用来对SQL中查询结果集进行指定顺序排序。
函数使用格式如下：order by （str，str1，str2，str3，str4……），str与str1，str2，str3，str4比较，其中str指的是字段名字，意为：字段str按照字符串str1，str2，str3，str4的顺序返回查询到的结果集。
如果表中str字段值不存在于str1，str2，str3，str4中的记录，放在结果集最前面返回。
带关键字的语法
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
关键字的执行优先级
mysql查询时的书写顺序
select..distinct..字段名...from...where...group by...having...order by...limit..
mysql查询时的执行顺序
重点中的重点：关键字的执行优先级 from where group by having select distinct order by limit
1.找到表:from
2.拿着where指定的约束条件，去文件/表中取出一条条记录
3.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
4.将分组的结果进行having过滤
5.执行select,查看结果集中的哪个列，或列的计算结果
6.去重复
7.将结果按条件排序：order by
8.限制结果的显示条数
需要注意的点
from后面的表关联，是自右向左解析的 而where条件的解析顺序是自下而上的。 也就是说，在写SQL文的时候，尽量把数据量小的表放在最右边来进行关联（用小表去匹配大表）， 而把能筛选出小量数据的条件放在where语句的最左边 （用小表去匹配大表）
简单查询
准备表和记录
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 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', #大部分是男的 age int(3) unsigned not null default 28, hire_date date not null, post varchar(50), post_comment varchar(100), salary double(15,2), #双精度浮点数（非准确小数值），参数15是数字总个数，2是小数点后个数 office int, #一个部门一个屋子 depart_id int ); #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 | | +--------------+-----------------------+------+-----+---------+----------------+ 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 ('xiong1','male',18,'20170301','外交大使',7300.33,401,1), #以下是教学部 ('xiong2','male',78,'20150302','teacher',1000000.31,401,1), ('xiong3','male',81,'20130305','teacher',8300,401,1), ('xiong4','male',73,'20140701','teacher',3500,401,1), ('xiong5','male',28,'20121101','teacher',2100,401,1), ('xiong6','female',18,'20110211','teacher',9000,401,1), ('xiong7','male',18,'19000301','teacher',30000,401,1), ('xiong8','male',48,'20101111','teacher',10000,401,1), ('dog1','female',48,'20150311','sale',3000.13,402,2),#以下是销售部门 ('dog2','female',38,'20101101','sale',2000.35,402,2), ('dog3','female',18,'20110312','sale',1000.37,402,2), ('dog4','female',18,'20160513','sale',3000.29,402,2), ('dog5','female',28,'20170127','sale',4000.33,402,2), ('miao1','male',28,'20160311','operation',10000.13,403,3), #以下是运营部门 ('miao2','male',18,'19970312','operation',20000,403,3), ('miao3','female',18,'20130311','operation',19000,403,3), ('miao4','male',18,'20150411','operation',18000,403,3), ('miao5','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
简单查询
简单查询
select id,name,sex,age,hire_date,post,post_comment,salary,office,depart_id
from employee;
select * from employee;
select name,salary from employee;
避免重复distinct
select distinct post from employee;
通过四则运算查询
select name, salary*12 from employee;
select name, salary*12 as Annual_salary from employee;
select name, salary*12 Annual_salary from employee;
定义显示格式
concat() 函数用于连接字符串
写法一
select concat('姓名: ',name,' 年薪: ', salary*12) as Annual_salary
from employee;
写法二
select concat('姓名: ',name) as 姓名,concat('年薪: ',salary) as 年薪 from employee; #注意逗号不能敲成中文的
CONCAT_WS() 第一个参数为分隔符，
SELECT CONCAT_WS(':',name,salary*12) AS Annual_salary
FROM employee;
结合CASE语句：
SELECT
(
CASE
WHEN NAME = 'xiong1' THEN
NAME
WHEN NAME = 'xiong2' THEN
CONCAT(name,'_BIGSB')
ELSE
concat(NAME, 'SB')
END
) as new_name
FROM
emp;
补充：case when语句的详细分析
case when语句，用于计算条件列表并返回多个可能结果表达式之一。 CASE 具有两种格式：简单 CASE 函数将某个表达式与一组简单表达式进行比较以确定结果。
CASE 搜索函数计算一组布尔表达式以确定结果。 两种格式都支持可选的 ELSE 参数 简单的case函数 CASE input_expression WHEN when_expression THEN result_expression [...n ] [ ELSE else_result_expression END 参数介绍： input_expression是使用简单 CASE 格式时所计算的表达式。Input_expression 是任何有效的 Microsoft SQL Server 表达式。 WHEN when_expression使用简单 CASE 格式时 input_expression 所比较的简单表达式。When_expression 是任意有效的 SQL Server 表达式。Input_expression 和每个 when_expression 的数据类型必须相同，或者是隐性转换。 占位符，表明可以使用多个 WHEN when_expression THEN result_expression 子句或 WHEN Boolean_expression THEN result_expression 子句。 THEN result_expression 当 input_expression = when_expression 取值为 TRUE，或者 Boolean_expression 取值 TRUE 时返回的表达式。 result expression 是任意有效的 SQL Server 表达式。 ELSE else_result_expression当比较运算取值不为 TRUE 时返回的表达式。如果省略此参数并且比较运算取值不为 TRUE，CASE 将返回 NULL 值。else_result_expression 是任意有效的 SQL Server 表达式。else_result_expression 和所有 result_expression 的数据类型必须相同，或者必须是隐性转换。 1 简单 CASE 函数：返回结果值介绍： 计算 input_expression，然后按指定顺序对每个 WHEN 子句的 input_expression = when_expression 进行计算。 返回第一个取值为 TRUE 的 (input_expression = when_expression) 的 result_expression。如果没有取值为 TRUE 的 input_expression = when_expression，则当指定 ELSE 子句时 SQL Server 将返回 else_result_expression；若没有指定 ELSE 子句，则返回 NULL 值。 2 CASE 搜索函数 CASE WHEN Boolean_expression THEN result_expression [...n ] [ ELSE else_result_expression END 参数介绍： WHEN Boolean_expression 使用 CASE 搜索格式时所计算的布尔表达式。Boolean_expression 是任意有效的布尔表达式。结果类型从 result_expressions 和可选 else_result_expression 的类型集合中返回最高的优先规则类型。有关更多信息，请参见数据类型的优先顺序。 CASE 搜索函数：返回结果值介绍： 按指定顺序为每个 WHEN 子句的 Boolean_expression 求值。返回第一个取值为 TRUE 的 Boolean_expression 的 result_expression。 如果没有取值为 TRUE 的 Boolean_expression，则当指定 ELSE 子句时 SQL Server 将返回 else_result_expression；若没有指定 ELSE 子句，则返回 NULL 值。 3、CASE 可能是 SQL 中被误用最多的关键字之一 虽然，可能以前用过这个关键字来创建字段，但是它还具有更多用法。 例如，可以在 WHERE 子句中使用 CASE。或者在 GROUP BY 子句中使用 CASE 使用CASE WHEN进行字符串替换处理,稍加深入，还可以得到以前认为不可能得到的分组排序结果集 4 其他 简单语句 多重语句 在SELECT查询中使用CASE WHEN
练习
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
select concat('<名字:',name,'> ','<薪资:',salary,'>') from employee;
select distinct depart_id from employee;
select name,salary*12 annual_salary from employee;
WHERE约束
where字句中可以使用：
1. 比较运算符：> < >= <= <> !=
2. between 80 and 100 值在10到20之间
3. in(80,90,100) 值是10或20或30
4. like 'egon%'
pattern可以是%或_，
%表示任意多字符
_表示一个字符
select name from employee where name like 'xiong%';
5. 逻辑运算符：在多个条件直接可以使用逻辑运算符 and or not
regex
any
all
1:单条件查询
SELECT name FROM employee
WHERE post='sale';
2:多条件查询
SELECT name,salary FROM employee
WHERE post='teacher' AND salary>10000;
3:关键字BETWEEN AND
SELECT name,salary FROM employee
WHERE salary BETWEEN 10000 AND 20000;
SELECT name,salary FROM employee
WHERE salary NOT BETWEEN 10000 AND 20000;
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;
SELECT name,post_comment FROM employee
WHERE post_comment IS NOT NULL;
SELECT name,post_comment FROM employee
WHERE post_comment=''; 注意''是空字符串，不是null
ps：
执行
update employee set post_comment='' where id=2;
再用上条查看，就会有结果了
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) ;
SELECT name,salary FROM employee
WHERE salary NOT IN (3000,3500,4000,9000) ;
6:关键字like模糊查询
通配符’%’
SELECT * FROM employee
WHERE name LIKE 'eg%';
通配符’_’
SELECT * FROM employee
WHERE name LIKE 'al__';
练习
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%';
分组查询:GROUP BY
什么是分组，为什么要分组？
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 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？
数据库中分组是为了统计
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也即重复性比较高的字段 4、大前提： 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，其他都被隐藏了 如果想查看组内信息，需要借助于聚合函数!!!
ONLY_FULL GROUP_BY
#查看MySQL 5.7默认的sql_mode如下： mysql> select @@global.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 #！！！注意 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， 要么是来自于group by list中的表达式的值。 #设置sql_mole如下操作(我们可以去掉ONLY_FULL_GROUP_BY模式)： mysql> set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE, ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION'; ！！！SQL_MODE设置！！！
mysql> select @@global.sql_mode; +-------------------+ | @@global.sql_mode | +-------------------+ | | +-------------------+ row in set (0.00 sec) mysql> select * from emp group by post; +----+--------+--------+-----+------------+-----------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+--------+--------+-----+------------+-----------+--------------+------------+--------+-----------+ | 14 | miao1 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 9 | dog1 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 2 | xiong2 | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 1 | xiong1 | male | 18 | 2017-03-01 | 外交大使 | NULL | 7300.33 | 401 | 1 | +----+--------+--------+-----+------------+-----------+--------------+------------+--------+-----------+ 4 rows in set (0.00 sec) #由于没有设置ONLY_FULL_GROUP_BY,于是也可以有结果，默认都是组内的第一条记录，但其实这是没有意义的 mysql> set global sql_mode='ONLY_FULL_GROUP_BY'; Query OK, 0 rows affected (0.00 sec) mysql> quit #设置成功后，一定要退出，然后重新登录方可生效 Bye mysql> use db1; Database changed mysql> select * from emp group by post; #报错 ERROR 1055 (42000): 'db1.emp.id' isn't in GROUP BY mysql> select post,count(id) from emp 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 | | 外交大使 | 1 | +-----------+-----------+ 4 rows in set (0.03 sec)
GROUP BY
应该注意的一些点
单独使用GROUP BY关键字分组
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 使用了GROUP_CONCAT()之后，就可以看到组内所有的记录，但是这条记录是默认用逗号拼接而成的
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;
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人
强调： 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
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
示例：
SELECT COUNT(*) FROM employee;
SELECT COUNT(*) FROM employee WHERE depart_id=1;
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=3;
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1：分组 mysql> select post,group_concat(name) from employee group by post; +-----------+--------------------------------------------------+ | post | group_concat(name) | +-----------+--------------------------------------------------+ | operation | miao1,miao2,miao3,miao4,miao5 | | sale | dog1,dog2,dog3,dog4,dog5 | | teacher | xiong2,xiong3,xiong4,xiong5,xiong6,xiong7,xiong8 | | 外交大使 | xiong1 | +-----------+--------------------------------------------------+ 4 rows in set (0.00 sec) 题目2： mysql> select post,count(id) from employee group by post; +-----------+-----------+ | post | count(id) | +-----------+-----------+ | operation | 5 | | sale | 5 | | teacher | 7 | | 外交大使 | 1 | +-----------+-----------+ 4 rows in set (0.00 sec) 题目3： mysql> select sex,count(id) from employee group by sex; +--------+-----------+ | sex | count(id) | +--------+-----------+ | male | 10 | | female | 8 | +--------+-----------+ 2 rows in set (0.00 sec) 题目4： mysql> select post,avg(salary) from employee group by post; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.026000 | | sale | 2600.294000 | | teacher | 151842.901429 | | 外交大使 | 7300.330000 | +-----------+---------------+ 4 rows in set (0.00 sec) 题目5 mysql> select post,max(salary) from employee group by post; +-----------+-------------+ | post | max(salary) | +-----------+-------------+ | operation | 20000.00 | | sale | 4000.33 | | teacher | 1000000.31 | | 外交大使 | 7300.33 | +-----------+-------------+ 4 rows in set (0.04 sec) 题目6 mysql> select post,min(salary) from employee group by post; +-----------+-------------+ | post | min(salary) | +-----------+-------------+ | operation | 10000.13 | | sale | 1000.37 | | teacher | 2100.00 | | 外交大使 | 7300.33 | +-----------+-------------+ 4 rows in set (0.00 sec) 题目七 mysql> select sex,avg(salary) from employee group by sex; +--------+---------------+ | sex | avg(salary) | +--------+---------------+ | male | 110920.077000 | | female | 7250.183750 | +--------+---------------+
HAVING过滤
HAVING与WHERE不一样的地方在于
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,可以使用聚合函数
mysql> select @@sql_mode; +--------------------+ | @@sql_mode | +--------------------+ | ONLY_FULL_GROUP_BY | +--------------------+ 1 row in set (0.00 sec) 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 | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ 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 salary > 10000;#错误，分组后无法直接取到salary字段 ERROR 1054 (42S22): Unknown column 'salary' in 'having clause' mysql> select post,group_concat(name) from employee group by post having avg(salary) > 10000; +-----------+--------------------------------------------------+ | post | group_concat(name) | +-----------+--------------------------------------------------+ | operation | miao1,miao2,miao3,miao4,miao5 | | teacher | xiong2,xiong3,xiong4,xiong5,xiong6,xiong7,xiong8 | +-----------+--------------------------------------------------+ 2 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) from employee group by post having count(id) < 2; +----------+--------------------+-----------+ | post | group_concat(name) | count(id) | +----------+--------------------+-----------+ | 外交大使 | xiong1 | 1 | +----------+--------------------+-----------+ 1 row in set (0.00 sec) 题目2： mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.026000 | | teacher | 151842.901429 | +-----------+---------------+ 题目3： mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 and avg(salary) <20000; +-----------+--------------+ | post | avg(salary) | +-----------+--------------+ | operation | 16800.026000 | +-----------+--------------+
查询排序:ORDER BY
按单列排序
SELECT * FROM employee ORDER BY salary;
SELECT * FROM employee ORDER BY salary ASC;
SELECT * 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 * from employee
ORDER BY age,
salary DESC;
补充
用 DESC 表示按倒序排序(即：从大到小排序) ---降序排列 用 ACS 表示按正序排序(即：从小到大排序)---升序排列
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; #题目2 mysql> select post,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 | +-----------+---------------+ #题目3 mysql> select post,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 | +-----------+---------------+
限制查询的记录数:LIMIT
SELECT * FROM employee ORDER BY salary DESC
LIMIT 3; #默认初始位置为0，读三条记录
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
分页显示，每页5条
mysql> select * from employee limit 0,5; +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 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 | | 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 | +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ 5 rows in set (0.00 sec) mysql> select * from employee limit 5,5; +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | 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 | | 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 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ 5 rows in set (0.00 sec) mysql> select * from employee limit 10,5; +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | 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 | | 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 | +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ 5 rows in set (0.00 sec)
使用正则表达式查询
SELECT * FROM employee WHERE name REGEXP '^ale';
SELECT * FROM employee WHERE name REGEXP 'on$';
SELECT * FROM employee WHERE name REGEXP 'm{2}';
小结：对字符串匹配的方式
WHERE name = 'egon';
WHERE name LIKE 'yua%';
WHERE name REGEXP 'on$';
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
select * from employee where name regexp '^jin.*[gn]$';