1.如何找出两张表之间的关系
先站在左表的角度去找 , 是否左表的多条记录可以对应右表的一条记录，如果是，则证明左表的一个字段foreign key 右表一个字段（通常是id）
再站在右表的角度去找 , 是否右表的多条记录可以对应左表的一条记录，如果是，则证明右表的一个字段foreign key 左表一个字段（通常是id）
总结:
多对一:
如果只有步骤1成立，则是左表多对一右表 , 如果只有步骤2成立，则是右表多对一左表
多对多:
如果步骤1和2同时成立，则证明这两张表时一个双向的多对一，即多对多,需要定义一个这两张表的关系表来专门存放二者的关系
一对一:
如果1和2都不成立，而是左表的一条记录唯一对应右表的一条记录，反之亦然。这种情况很简单，就是在左表foreign key右表的基础上，将左表的外键字段设置成unique即可
2.表的三种关系
一对多(或者多对一):
关联方式: foreign key
create table press( id int primary key auto_increment, name varchar(20) ); create table book( id int primary key auto_increment, name varchar(20), press_id int not null, constraint fk_book_press foreign key(press_id) references press(id) on delete cascade on update cascade ); # 先往被关联表中插入记录 insert into press(name) values
('北京工业地雷出版社'), ('人民音乐不好听出版社'), ('知识产权没有用出版社') ; # 再往关联表中插入记录 insert into book (name,press_id) alues ('九阳神功',1), ('九阴真经',2), ('九阴白骨爪',2), ('独孤九剑',3), ('降龙十巴掌',2), ('葵花宝典',3) ; 查询结果: select * from book; select * from press;
多对多:
关联方式: foreign key +一张新的表
create table book( id int primary key auto_increment, name varchar(20) ); create table author( id int primary key auto_increment, name varchar(20) ); create table autho_book( id int primary key auto_increment, book_id int not null, author_id int not null, constraint fk_book foreign key(book_id) references book(id) on delete cascade on update cascade, constraint fk_author foreign key(author_id) references author(id) on delete cascade on update cascade ); insert into author(name) values('egon'),('alex'),('wusir'),('yuanhao'); insert into book(name) values ('九阳神功'), ('九阴真经'), ('九阴白骨爪'), ('独孤九剑'), ('降龙十巴掌'), ('葵花宝典'); insert into autho_book(author_id,book_id) values (1,1), (1,2), (1,3), (1,4), (1,5), (1,6), (2,1), (2,6), (3,4), (3,5), (3,6), (4,1) ;
一对一;
关联方式: foreign key +unique
#例如： 一个用户只能注册一个博客 #两张表： 用户表 （user）和 博客表(blog) # 创建用户表 create table user( id int primary key auto_increment, name varchar(20) ); # 创建博客表 create table blog( id int primary key auto_increment, url varchar(100), user_id int unique, constraint fk_user foreign key(user_id) references user(id) on delete cascade on update cascade ); #插入用户表中的记录 insert into user(name) values ('alex'), ('wusir'), ('egon'), ('xiaoma') ; # 插入博客表的记录 insert into blog(url,user_id) values ('http://www.cnblog/alex',1), ('http://www.cnblog/wusir',2), ('http://www.cnblog/egon',3), ('http://www.cnblog/xiaoma',4) ; # 查询wusir的博客地址 select url from blog where user_id=2;
二.数据的增删改
在mysql管理软件中,可以通过sql语句中的DML语言来实现数据的操作,包括
1.使用insert 实现数据的插入
2.update 实现数据的更新
3.使用delete 实现数据的删除
4.使用select 查询数据
插入数据 INSERT
1.查完整的数据(顺序插入)
语法一:
inert into 表名(字段1,字段2, 字段3,..) values(值1,值2,值3,...);
语法二:
insert into 表名 values (值1,值2, 值3,...);
2.指定字段插入数据
语法:
inert into 表名(字段1,字段2, 字段3,..) values(值1,值2,值3,...);
3.插入多条记录
语法:
INSERT INTO 表名 VALUES (值1,值2,值3…值n), (值1,值2,值3…值n), (值1,值2,值3…值n);
4.插入查询结果
语法:
insert into 表名(字段1,字段2,字段3,...)
select (字段1,字段2,字段3,...) from 表2
whert ..;
数据更新 UPDATE
语法:
update 表名 set
字段1=值1,
字段2=值2,
where condition;
示例:
update mysql.user set password=password("123")
where user="root" and host="localhost";
删除数据 delete
语法:
delete from 表名
where conition;
示例:
delete from mysql.user
where password="";
三.单表查询
语法:
1.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
2.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
6.去重
7.将结果按条件排序：order by
8.限制结果的显示条数
创建员工表,表的字段和数据类型
company.employee
员工id id int
姓名 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,设置字段的约束条件 create table employee( id int primary key 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), office int,#一个部门一个屋 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 | | emp_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 | | | salart | double(15,2) | YES | | NULL | | | office | int(11) | YES | | NULL | | | depart_id | int(11) | YES | | NULL | | +--------------+-----------------------+------+-----+---------+----------------+ 10 rows in set (0.08 sec) #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), ('xiaomage','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) ;
where 约束
where子句中可以使用
1.比较运算符：>、<、>=、<=、!=
2.between 80 and 100 ：值在80到100之间
3.in(80,90,100)值是10或20或30
4.like 'xiaomagepattern': pattern可以是%或者_。%小时任意多字符，_表示一个字符
5.逻辑运算符：在多个条件直接可以使用逻辑运算符 and or
验证结果:
#1 :单条件查询 mysql> select id,emp_name from employee where id > 5; +----+------------+ | id | emp_name | +----+------------+ | 6 | jingliyang | | 7 | jinxin | | 8 | xiaomage | | 9 | 歪歪 | | 10 | 丫丫 | | 11 | 丁丁 | | 12 | 星星 | | 13 | 格格 | | 14 | 张野 | | 15 | 程咬金 | | 16 | 程咬银 | | 17 | 程咬铜 | | 18 | 程咬铁 | #2 多条件查询 mysql> select emp_name from employee where post='teacher' and salary>10000; +----------+ | emp_name | +----------+ | alex | | jinxin | +----------+ #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; #注意''是空字符串，不是null SELECT name,post_comment FROM employee WHERE post_comment=''; 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 mysql> SELECT name,salary FROM employee WHERE salary=3000 OR salary=3500 OR salary=4000 OR salary=9000 ; +------------+---------+ | name | salary | +------------+---------+ | yuanhao | 3500.00 | | jingliyang | 9000.00 | +------------+---------+ rows in set (0.00 sec) mysql> SELECT name,salary FROM employee WHERE salary IN (3000,3500,4000,9000) ; +------------+---------+ | name | salary | +------------+---------+ | yuanhao | 3500.00 | | jingliyang | 9000.00 | +------------+---------+ mysql> SELECT name,salary FROM employee WHERE salary NOT IN (3000,3500,4000,9000) ; +-----------+------------+ | name | salary | +-----------+------------+ | egon | 7300.33 | | alex | 1000000.31 | | wupeiqi | 8300.00 | | liwenzhou | 2100.00 | | jinxin | 30000.00 | | xiaomage | 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 | +-----------+------------+ rows in set (0.00 sec) #6:关键字LIKE模糊查询 通配符’%’ mysql> SELECT * FROM employee WHERE name LIKE 'jin%'; +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | 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 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ rows in set (0.00 sec) 通配符'_' mysql> SELECT age FROM employee WHERE name LIKE 'ale_'; +-----+ | age | +-----+ | 78 | +-----+ row in set (0.00 sec) 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 #对应的sql语句 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%';
group by 分组查询
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？
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
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，如果想查看组内信息，需要借助于聚合函数
当执行以下sql语句的时候，是以post字段查询了组中的第一条数据，没有任何意义，因为我们现在想查出当前组的多条记录。
mysql> select * from employee group by post; +----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 2 | alex | male | 78 | 2015-03-02 | teacher | | 1000000.31 | 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 | +----+--------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ 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 如果想分组，则必须要设置全局的sql的模式为ONLY_FULL_GROUP_BY mysql> set global sql_mode='ONLY_FULL_GROUP_BY'; Query OK, 0 rows affected (0.00 sec) #查看MySQL 5.7默认的sql_mode如下： mysql> select @@global.sql_mode; +--------------------+ | @@global.sql_mode | +--------------------+ | ONLY_FULL_GROUP_BY | +--------------------+ row in set (0.00 sec) mysql> exit;#设置成功后，一定要退出，然后重新登录方可生效 Bye
继续验证通过group by分组之后，只能查看当前字段,如果想查看组内信息，需要借助于聚合函数
mysql> select * from emp group by post;# 报错 ERROR 1054 (42S22): Unknown column 'post' in 'group statement' 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 | +-----------------------------------------+ rows in set (0.00 sec)
聚合函数
max()求最大值 min()求最小值 avg()求平均值 sum() 求和 count() 求总个数 #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 # 每个部门有多少个员工 select post,count(id) from employee group by post; # 每个部门的最高薪水 select post,max(salary) from employee group by post; # 每个部门的最低薪水 select post,min(salary) from employee group by post; # 每个部门的平均薪水 select post,avg(salary) from employee group by post; # 每个部门的所有薪水 select post,sum(age) from employee group by post;
HAVING 过滤
having和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,可以使用聚合函数
验证:
mysql> select * from employee where salary>1000000; +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ row in set (0.00 sec) mysql> select * from employee having salary>1000000; ERROR 1463 (42000): Non-grouping field 'salary' is used in HAVING clause # 必须使用group by才能使用group_concat()函数，将所有的name值连接 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 'post' in 'field list'
练习
# 题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 mysql> select post,group_concat(name),count(id) from employee group by post; +-----------------------------------------+-----------------------------------------------------------+-----------+ | post | group_concat(name) | count(id) | +-----------------------------------------+-----------------------------------------------------------+-----------+ | 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 | xiaomage,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex | 7 | | 老男孩驻沙河办事处外交大使 | egon | 1 | +-----------------------------------------+-----------------------------------------------------------+-----------+ rows in set (0.00 sec) mysql> select post,group_concat(name),count(id) from employee group by post having count(id)<2; +-----------------------------------------+--------------------+-----------+ | post | group_concat(name) | count(id) | +-----------------------------------------+--------------------+-----------+ | 老男孩驻沙河办事处外交大使 | egon | 1 | +-----------------------------------------+--------------------+-----------+ row in set (0.00 sec) #题2：查询各岗位平均薪资大于10000的岗位名、平均工资 mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.026000 | | teacher | 151842.901429 | +-----------+---------------+ rows in set (0.00 sec) #题3：查询各岗位平均薪资大于10000且小于20000的岗位名、平均工资 mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 and avg(salary) <20000; +-----------+--------------+ | post | avg(salary) | +-----------+--------------+ | operation | 16800.026000 | +-----------+--------------+ row in set (0.00 sec)
order by 查询排序
单列排序
SELECT * FROM employee ORDER BY age;
SELECT * FROM employee ORDER BY age ASC;
SELECT * FROM employee ORDER BY age DESC;
按多列排序:先按照age升序排序，如果年纪相同，则按照id降序
SELECT * from employee
ORDER BY age ASC,
id DESC;
验证:
SELECT * from employee ORDER BY age ASC,id DESC; mysql> SELECT * from employee ORDER BY age ASC,id DESC; +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 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 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 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 | | 14 | 张野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 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 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 8 | xiaomage | 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 | | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | +----+------------+--------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ rows in set (0.01 sec) mysql>
练习
# 题目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 select * from employee ORDER BY age asc,hire_date desc; # 题目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 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 | +-----------+---------------+ rows in set (0.00 sec) # 题目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 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 | +-----------+---------------+ rows in set (0.00 sec) mysql>
limit 限制查询的记录数
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
练习:
# 第1页数据 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 | +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ rows in set (0.00 sec) # 第2页数据 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 | xiaomage | 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 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ rows in set (0.00 sec) # 第3页数据 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 | +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ rows in set (0.00 sec)