day06-单表查询
2024-10-14 06:58:08
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（重点）
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
6.去重distinct
7.将结果按条件排序：order by
8.限制结果的显示条数
创建公司员工表，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 创建员工表，并插入记录
#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 | |
+--------------+-----------------------+------+-----+---------+----------------+ #三个部门：教学，销售，运营
insert into employee(name ,sex,age,hire_date,post,salary,office,depart_id) values
('mike','male',28,'','teacher',7300.33,401,1), #以下是教学部
('jack','male',30,'','teacher',1000000.31,401,1),
('tom','male',21,'','teacher',8300,401,1),
('lucy','male',25,'','teacher',3500,401,1),
('alice','male',28,'','teacher',2100,401,1),
('frank','female',18,'','teacher',2000,401,1),
('lilei','male',28,'','teacher',30000,401,1),
('hanmeimei','female',28,'','teacher',10000,401,1), ('小美','female',48,'','sale',3000.13,402,2),#以下是销售部门
('小花','female',38,'','sale',2000.35,402,2),
('小草','female',18,'','sale',1000.37,402,2),
('小星','female',18,'','sale',3000.29,402,2),
('小月','female',28,'','sale',4000.33,402,2), ('程咬金','male',18,'','operation',20000,403,3),#以下是运营部门
('程咬银','female',18,'','operation',19000,403,3),
('程咬铜','male',18,'','operation',18000,403,3),
('程咬铁','female',18,'','operation',17000,403,3); # 查看表数据
mysql> select * from employee;
+----+-----------+--------+-----+------------+-----------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+------------+--------+-----------+
| 1 | mike | male | 28 | 2012-03-01 | teacher | NULL | 7300.33 | 401 | 1 |
| 2 | jack | male | 30 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 |
| 3 | tom | male | 21 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | lucy | male | 25 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | alice | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 6 | frank | female | 18 | 2018-02-11 | teacher | NULL | 2000.00 | 401 | 1 |
| 7 | lilei | male | 28 | 2012-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | hanmeimei | female | 28 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 小美 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 小花 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 11 | 小草 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 小星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 13 | 小月 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 15 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 16 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 17 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------+--------------+------------+--------+-----------+
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(10,20,30)值是10或20或30
4.like 'tom&' line 'tom_': %表示任意多个字符，_表示任意一个字符
5.逻辑运算符：多个条件可以使用逻辑运算符 and or not
验证结果：
1.单条件查询
#查询id>5的所有id和name
mysql> select id, name from employee where id>5;
+----+-----------+
| id | name |
+----+-----------+
| 6 | frank |
| 7 | lilei |
| 8 | hanmeimei |
| 9 | 小美 |
| 10 | 小花 |
| 11 | 小草 |
| 12 | 小星 |
| 13 | 小月 |
| 14 | 程咬金 |
| 15 | 程咬银 |
| 16 | 程咬铜 |
| 17 | 程咬铁 |
+----+-----------+
2.多条件查询
#查询职位是teacher，并且薪资大于10000的所有name
mysql> select name from employee where post='teacher' and salary>10000;
+-------+
| name |
+-------+
| jack |
| lilei |
+-------+
3.关键字between、and
#查询薪资在10000到20000之间的所有name
mysql> select name, salary from employee where salary between 10000 and 20000;
+-----------+----------+
| name | salary |
+-----------+----------+
| hanmeimei | 10000.00 |
| 程咬金 | 20000.00 |
| 程咬银 | 19000.00 |
| 程咬铜 | 18000.00 |
| 程咬铁 | 17000.00 |
+-----------+----------+ #注意''是空字符串，不是null，所以查询post_comment是''时并不能查询到结果
mysql> select name, post_comment from employee where post_comment='';
Empty set (0.00 sec) 执行update再查询就有结果了
mysql> update employee set post_comment='' where id=2;
Query OK, 1 row affected (0.02 sec)
Rows matched: 1 Changed: 1 Warnings: 0 mysql> select name, post_comment from employee where post_comment='';
+------+--------------+
| name | post_comment |
+------+--------------+
| jack | |
+------+--------------+
4.关键字in、not in集合查询
mysql> select name, salary from employee where salary=10000 or salary=20000 or salary=30000;
+-----------+----------+
| name | salary |
+-----------+----------+
| lilei | 30000.00 |
| hanmeimei | 10000.00 |
| 程咬金 | 20000.00 |
+-----------+----------+ mysql> select name, salary from employee where salary in (10000,20000,30000);
+-----------+----------+
| name | salary |
+-----------+----------+
| lilei | 30000.00 |
| hanmeimei | 10000.00 |
| 程咬金 | 20000.00 |
+-----------+----------+ mysql> select name, salary from employee where salary not in (10000,20000,30000);
+-----------+------------+
| name | salary |
+-----------+------------+
| mike | 7300.33 |
| jack | 1000000.31 |
| tom | 8300.00 |
| lucy | 3500.00 |
| alice | 2100.00 |
| frank | 2000.00 |
| 小美 | 3000.13 |
| 小花 | 2000.35 |
| 小草 | 1000.37 |
| 小星 | 3000.29 |
| 小月 | 4000.33 |
| 程咬银 | 19000.00 |
| 程咬铜 | 18000.00 |
| 程咬铁 | 17000.00 |
+-----------+------------+
5.关键字LIKE模糊查询
%表示任意多个字符，_表示任意一个字符 mysql> select * from employee where name like '%m%';
+----+-----------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| 1 | mike | male | 28 | 2012-03-01 | teacher | NULL | 7300.33 | 401 | 1 |
| 3 | tom | male | 21 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 8 | hanmeimei | female | 28 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
+----+-----------+--------+-----+------------+---------+--------------+----------+--------+-----------+
3 rows in set (0.00 sec) mysql> select * from employee where name like 'm%';
+----+------+------+-----+------------+---------+--------------+---------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+---------+--------+-----------+
| 1 | mike | male | 28 | 2012-03-01 | teacher | NULL | 7300.33 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+---------+--------+-----------+
1 row in set (0.00 sec) mysql> select * from employee where name like 'to_';
+----+------+------+-----+------------+---------+--------------+---------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+---------+--------+-----------+
| 3 | tom | male | 21 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+---------+--------+-----------+
1 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25岁的员工姓名、年龄
3. 查看岗位是teacher且薪资在9000-10000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t开头的员工姓名、年薪
对应的sql语句
mysql> select name,age from employee where post='teacher';
+-----------+-----+
| name | age |
+-----------+-----+
| mike | 28 |
| jack | 30 |
| tom | 21 |
| lucy | 25 |
| alice | 28 |
| frank | 18 |
| lilei | 28 |
| hanmeimei | 28 |
+-----------+-----+ mysql> select name,age from employee where post='teacher' and age>25;
+-----------+-----+
| name | age |
+-----------+-----+
| mike | 28 |
| jack | 30 |
| alice | 28 |
| lilei | 28 |
| hanmeimei | 28 |
+-----------+-----+ mysql> select name,age,salary from employee where post='teacher' and salary between 9000 and 10000;
+-----------+-----+----------+
| name | age | salary |
+-----------+-----+----------+
| hanmeimei | 28 | 10000.00 |
+-----------+-----+----------+ mysql> select * from employee where post_comment is not null;
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| 2 | jack | male | 30 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ mysql> select name,age,salary from employee where salary in (9000, 10000,30000);
+-----------+-----+----------+
| name | age | salary |
+-----------+-----+----------+
| lilei | 28 | 30000.00 |
| hanmeimei | 28 | 10000.00 |
+-----------+-----+----------+ mysql> select name,age,salary from employee where salary not in (9000, 10000,30000);
+-----------+-----+------------+
| name | age | salary |
+-----------+-----+------------+
| mike | 28 | 7300.33 |
| jack | 30 | 1000000.31 |
| tom | 21 | 8300.00 |
| lucy | 25 | 3500.00 |
| alice | 28 | 2100.00 |
| frank | 18 | 2000.00 |
| 小美 | 48 | 3000.13 |
| 小花 | 38 | 2000.35 |
| 小草 | 18 | 1000.37 |
| 小星 | 18 | 3000.29 |
| 小月 | 28 | 4000.33 |
| 程咬金 | 18 | 20000.00 |
| 程咬银 | 18 | 19000.00 |
| 程咬铜 | 18 | 18000.00 |
| 程咬铁 | 18 | 17000.00 |
+-----------+-----+------------+ mysql> select name,salary from employee where post='teacher' and name like 't%';
+------+---------+
| name | salary |
+------+---------+
| tom | 8300.00 |
+------+---------+
4、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。
#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 |
+--------------------+
1 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 |
+-----------------------------------------+
4 rows in set (0.00 sec)
5、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
mysql> select post, count(id) from employee group by post;
+-----------+-----------+
| post | count(id) |
+-----------+-----------+
| operation | 4 |
| sale | 5 |
| teacher | 8 |
+-----------+-----------+ # 每个部门的最高薪水
mysql> select post, max(salary) from employee group by post;
+-----------+-------------+
| post | max(salary) |
+-----------+-------------+
| operation | 20000.00 |
| sale | 4000.33 |
| teacher | 1000000.31 |
+-----------+-------------+ # 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;
6、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
验证：
mysql> select * from employee where salary>1000000;
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+
| 2 | jack | male | 30 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 |
+----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ 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 employee 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'
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
2. 查询各岗位平均薪资大于10000的岗位名、平均工资
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
#1、
mysql> select post, count(id), group_concat(name) from employee group by post;
+-----------+-----------+------------------------------------------------+
| post | count(id) | group_concat(name) |
+-----------+-----------+------------------------------------------------+
| operation | 4 | 程咬铁,程咬铜,程咬银,程咬金 |
| sale | 5 | 小月,小星,小草,小花,小美 |
| teacher | 8 | hanmeimei,lilei,frank,alice,lucy,tom,jack,mike |
+-----------+-----------+------------------------------------------------+ #2、
mysql> select post, avg(salary) from employee group by post having avg(salary) >10000;
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| operation | 18500.000000 |
| teacher | 132900.080000 | #3、
mysql> select post, avg(salary) from employee group by post having avg(salary) between 10000 and 20000;;
+-----------+--------------+
| post | avg(salary) |
+-----------+--------------+
| operation | 18500.000000 |
+-----------+--------------+
7、order by查询排序
按单列排序 asc升序（默认）， desc(降序）
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;
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
#1、
mysql> select * from employee order by age, hire_date desc;
+----+-----------+--------+-----+------------+-----------+--------------+------------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+------------+--------+-----------+
| 6 | frank | female | 18 | 2018-02-11 | teacher | NULL | 2000.00 | 401 | 1 |
| 12 | 小星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 16 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 17 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
| 15 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
| 11 | 小草 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 14 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 3 | tom | male | 21 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | lucy | male | 25 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 13 | 小月 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 5 | alice | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
| 1 | mike | male | 28 | 2012-03-01 | teacher | NULL | 7300.33 | 401 | 1 |
| 7 | lilei | male | 28 | 2012-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | hanmeimei | female | 28 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 2 | jack | male | 30 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 |
| 10 | 小花 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 |
| 9 | 小美 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
+----+-----------+--------+-----+------------+-----------+--------------+------------+--------+-----------+
17 rows in set (0.00 sec) #2、
mysql> select post, avg(salary) from employee group by post having avg(salary)>10000 order by avg(salary);
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| operation | 18500.000000 |
| teacher | 132900.080000 |
+-----------+---------------+ #3、
mysql> select post, avg(salary) from employee group by post having avg(salary)>10000 order by avg(salary) desc;
+-----------+---------------+
| post | avg(salary) |
+-----------+---------------+
| teacher | 132900.080000 |
| operation | 18500.000000 |
+-----------+---------------+
8、limit限制查询的记录数量
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：
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 | mike | male | 28 | 2012-03-01 | teacher | NULL | 7300.33 | 401 | 1 |
| 2 | jack | male | 30 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 |
| 3 | tom | male | 21 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 |
| 4 | lucy | male | 25 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 |
| 5 | alice | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 |
+----+-------+------+-----+------------+---------+--------------+------------+--------+-----------+
5 rows in set (0.05 sec) mysql> select * from employee limit 5,5;
+----+-----------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+---------+--------------+----------+--------+-----------+
| 6 | frank | female | 18 | 2018-02-11 | teacher | NULL | 2000.00 | 401 | 1 |
| 7 | lilei | male | 28 | 2012-03-01 | teacher | NULL | 30000.00 | 401 | 1 |
| 8 | hanmeimei | female | 28 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 |
| 9 | 小美 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 |
| 10 | 小花 | 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 | 小草 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 |
| 12 | 小星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 |
| 13 | 小月 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 |
| 14 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 |
| 15 | 程咬银 | female | 18 | 2013-03-11 | operation | NULL | 19000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
5 rows in set (0.00 sec) mysql> select * from employee limit 15,5;
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
| 16 | 程咬铜 | male | 18 | 2015-04-11 | operation | NULL | 18000.00 | 403 | 3 |
| 17 | 程咬铁 | female | 18 | 2014-05-12 | operation | NULL | 17000.00 | 403 | 3 |
+----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+
2 rows in set (0.00 sec)
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