文章目录

  • 1. 添加记录
  • 1.1 不指定字段名称
  • 1.2 一次插入多条记录
  • 1.3 INSERT ... SET 的形式
  • 2. 修改记录
  • 3. 删除记录
  • 4. 彻底清空数据表
  • 5. 查询记录
  • 5.1 WHERE条件进行查询
  • 5.2 检测null值
  • 5.3 [NOT]BETWEEN ...AND
  • 5.4 [NOT] IN()
  • 5.5 逻辑运算符 AND , OR, NOT
  • 5.6 [NOT] LIKE 模糊查询, 通配符 %, _
  • 5.7 GROUP BY
  • 5.8 group by 配合聚合函数来使用
  • 5.9 HAVING
  • 5.10 ORDER BY 排序
  • 5.11 随机打乱的函数
  • LIMIT 限制结果集显示条数,实现分页效果


1. 添加记录

先创建数据库和数据表

mysql> CREATE DATABASE IF NOT EXISTS king DEFAULT CHARACTER SET  'UTF8';
Query OK, 1 row affected, 1 warning (0.11 sec)

mysql> USE king;
Database changed
mysql> CREATE TABLE IF NOT EXISTS user(
    -> id INT UNSIGNED AUTO_INCREMENT KEY COMMENT '编号',
    -> username VARCHAR(20) NOT NULL UNIQUE COMMENT '用户名',
    -> age TINYINT UNSIGNED DEFAULT 18 COMMENT '年龄',
    -> email VARCHAR(50) NOT NULL DEFAULT '1111@qq.com' COMMENT '邮箱'
    -> )ENGINE=INNODB CHARSET=UTF8;
Query OK, 0 rows affected, 1 warning (1.43 sec)

mysql> SELECT DATEBASE;
ERROR 1054 (42S22): Unknown column 'DATEBASE' in 'field list'
mysql> SELECT DATEBASE();
ERROR 1305 (42000): FUNCTION king.DATEBASE does not exist
mysql> SELECT DATABASE();
+------------+
| DATABASE() |
+------------+
| king       |
+------------+
1 row in set (0.00 sec)

mysql> SHOW TABLES;
+----------------+
| Tables_in_king |
+----------------+
| user           |
+----------------+
1 row in set (0.02 sec)

mysql> DESC user;
+----------+------------------+------+-----+-------------+----------------+
| Field    | Type             | Null | Key | Default     | Extra          |
+----------+------------------+------+-----+-------------+----------------+
| id       | int unsigned     | NO   | PRI | NULL        | auto_increment |
| username | varchar(20)      | NO   | UNI | NULL        |                |
| age      | tinyint unsigned | YES  |     | 18          |                |
| email    | varchar(50)      | NO   |     | 1111@qq.com |                |
+----------+------------------+------+-----+-------------+----------------+
4 rows in set (0.00 sec)
1.1 不指定字段名称
mysql> INSERT user VALUE(1, 'KING', 24, '1212@qq.com');
Query OK, 1 row affected (0.07 sec)

mysql> INSERT user VALUES(NULL, 'queue', 25, 'queue@qq.com');
Query OK, 1 row affected (0.09 sec)

mysql> INSERT user VALUES(DEFAULT,'LILI', 26,  'lili@qq.com');
Query OK, 1 row affected (0.06 sec)

mysql> SELECT * FROM user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | KING     |   24 | 1212@qq.com  |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
+----+----------+------+--------------+
3 rows in set (0.00 sec)

列出指定字段,每一个字段与后边的值一一对应。

mysql> INSERT user(username, email) VALUES('rose', 'rose@qq.com');
Query OK, 1 row affected (0.09 sec)

mysql> INSERT user(username, age, email) VALUES('rosa', 20, 'rosa@qq.com');
Query OK, 1 row affected (0.05 sec)

mysql> SELECT * FROM user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | KING     |   24 | 1212@qq.com  |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
|  4 | rose     |   18 | rose@qq.com  |
|  6 | rosa     |   20 | rosa@qq.com  |
+----+----------+------+--------------+
5 rows in set (0.00 sec)
1.2 一次插入多条记录
mysql> INSERT user VALUES(NULL, 'a', DEFAULT, DEFAULT),
    -> (NULL, 'b', 56, 'b@qq.com'),
    -> (NULL, 'c', 34, 'c@qq.com');
Query OK, 3 rows affected (0.08 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | KING     |   24 | 1212@qq.com  |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
|  4 | rose     |   18 | rose@qq.com  |
|  6 | rosa     |   20 | rosa@qq.com  |
|  7 | a        |   18 | 1111@qq.com  |
|  8 | b        |   56 | b@qq.com     |
|  9 | c        |   34 | c@qq.com     |
+----+----------+------+--------------+
8 rows in set (0.00 sec)
1.3 INSERT … SET 的形式

INSERT tbl_name SET 字段名称=值, …;
一次只能插入一条记录

mysql> INSERT user SET username='d', age=45, email='d@qq.com';
Query OK, 1 row affected (0.06 sec)

mysql> SELECT * FROM user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | KING     |   24 | 1212@qq.com  |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
|  4 | rose     |   18 | rose@qq.com  |
|  6 | rosa     |   20 | rosa@qq.com  |
|  7 | a        |   18 | 1111@qq.com  |
|  8 | b        |   56 | b@qq.com     |
|  9 | c        |   34 | c@qq.com     |
| 10 | d        |   45 | d@qq.com     |
+----+----------+------+--------------+
9 rows in set (0.01 sec)

查数据库中的插入操作,如果为自动编号的字段赋值的话,我们可以用NULL或DEFAULT让其按照默认的递增的形式来实现。给有默认值的字段赋值时,可以用DEFAULT让其采用默认值。

2. 修改记录

语法:
UPDATE tbl_name SET 字段名称=值,字段名称=值[EHRER 条件]
如果不添加条件,整个表中的记录都会被更新

mysql> UPDATE user SET age=29 WHERE id=1;
Query OK, 1 row affected (0.09 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> SELECT * FROM user
    -> ;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | KING     |   29 | 1212@qq.com  |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
|  4 | rose     |   18 | rose@qq.com  |
|  6 | rosa     |   20 | rosa@qq.com  |
|  7 | a        |   18 | 1111@qq.com  |
|  8 | b        |   56 | b@qq.com     |
|  9 | c        |   34 | c@qq.com     |
| 10 | d        |   45 | d@qq.com     |
+----+----------+------+--------------+
9 rows in set (0.00 sec)
3. 删除记录

delete FROM tbl_name WHERE
如果不添加条件,表中所有字段都会被删除

mysql> DELETE FROM user WHERE username='KING';
Query OK, 1 row affected (0.08 sec)

mysql> SELECT * FROM user;
+----+----------+------+-------------+
| id | username | age  | email       |
+----+----------+------+-------------+
|  2 | queue    |   30 | 1111@qq.com |
|  3 | li       |   28 | 1111@qq.com |
|  4 | rose     |   23 | 1111@qq.com |
|  6 | rosa     |   30 | rosa@qq.com |
|  7 | a        |   28 | 1111@qq.com |
|  8 | b        |   66 | b@qq.com    |
|  9 | c        |   44 | c@qq.com    |
| 10 | d        |   55 | d@qq.com    |
+----+----------+------+-------------+
8 rows in set (0.03 sec)

mysql> SELECT * FROM user;
+----+----------+------+-------------+
| id | username | age  | email       |
+----+----------+------+-------------+
|  2 | queue    |   30 | 1111@qq.com |
|  3 | li       |   28 | 1111@qq.com |
|  4 | rose     |   23 | 1111@qq.com |
|  6 | rosa     |   30 | rosa@qq.com |
|  7 | a        |   28 | 1111@qq.com |
|  8 | b        |   66 | b@qq.com    |
|  9 | c        |   44 | c@qq.com    |
| 10 | d        |   55 | d@qq.com    |
+----+----------+------+-------------+
8 rows in set (0.03 sec)

mysql> DELETE FROM user;
Query OK, 6 rows affected (0.07 sec)

mysql> SELECT * FROM user;
Empty set (0.02 sec)

但是这样删除表数据后,对于自增长的字段,再你下次添加的时候,并不是从1开始的,

mysql> INSERT user VALUES(NULL, 'a', DEFAULT, DEFAULT),
    -> (NULL, 'b', 56, 'b@qq.com'),
    -> (NULL, 'c', 34, 'c@qq.com');
Query OK, 3 rows affected (0.10 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> SELECT * FROM user;
+----+----------+------+-------------+
| id | username | age  | email       |
+----+----------+------+-------------+
| 11 | a        |   18 | 1111@qq.com |
| 12 | b        |   56 | b@qq.com    |
| 13 | c        |   34 | c@qq.com    |
+----+----------+------+-------------+
3 rows in set (0.01 sec)

mysql> SHOW CREATE TABLE user;
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                                                                                                                                                                                                                                                                |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| user  | CREATE TABLE `user` (
  `id` int unsigned NOT NULL AUTO_INCREMENT COMMENT '编号',
  `username` varchar(20) NOT NULL COMMENT '用户名',
  `age` tinyint unsigned DEFAULT '18' COMMENT '年龄',
  `email` varchar(50) NOT NULL DEFAULT '1111@qq.com' COMMENT '邮箱',
  PRIMARY KEY (`id`),
  UNIQUE KEY `username` (`username`)
) ENGINE=InnoDB AUTO_INCREMENT=14 DEFAULT CHARSET=utf8          |
+-------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

想要下次插入数据时候,id值从1开始,就需要下面语句
ALTER TABLE user AUTO_INCREMENT=1;
(!!!注意,只有在删除表中所有数据后(DELETE FROM user),设置才有效)

mysql> DELETE FROM user;
Query OK, 4 rows affected (0.13 sec)

mysql> INSERT user VALUES(NULL, 'queue', 25, 'queue@qq.com');
Query OK, 1 row affected (0.07 sec)

mysql> SELECT * FROM user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | queue    |   25 | queue@qq.com |
+----+----------+------+--------------+
1 row in set (0.00 sec)
4. 彻底清空数据表

TRUNCATE [TABLE] tbl_name;
会清除表中所有记录,并重置AUTO_CREMENT的值

mysql> TRUNCATE user;
Query OK, 0 rows affected (0.85 sec)

mysql> SELECT * FROM user;
Empty set (0.08 sec)

mysql> INSERT user SET username='d', age=45, email='d@qq.com';
Query OK, 1 row affected (0.09 sec)

mysql> SELECT * FROM user;
+----+----------+------+----------+
| id | username | age  | email    |
+----+----------+------+----------+
|  1 | d        |   45 | d@qq.com |
+----+----------+------+----------+
1 row in set (0.00 sec)
5. 查询记录

mysql表a的数据覆盖到表b mysql表中数据_mysql

查询字段
SELECT select_expr, … FROM tbl_name
[WHERE 条件]
[GROUP BY {col_name | position} HAVING 二次筛选]
[ORDER BY {col_name | position | expr}{ASC | DESC}]
[LIMIT 限制结果集的显示条数]

*代表查询整个表中所有信息

mysql> SELECT * FROM user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | d        |   45 | d@qq.com     |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
|  6 | KING     |   24 | 1212@qq.com  |
+----+----------+------+--------------+
4 rows in set (0.00 sec)

mysql> SELECT username, age FROM user;
+----------+------+
| username | age  |
+----------+------+
| d        |   45 |
| queue    |   25 |
| LILI     |   26 |
| KING     |   24 |
+----------+------+
4 rows in set (0.00 sec)

可以使用库名.表名的形式查询数据,这样的好处是可以不用打开数据库
直接进行查询

mysql> SELECT * FROM king.user;
+----+----------+------+--------------+
| id | username | age  | email        |
+----+----------+------+--------------+
|  1 | d        |   45 | d@qq.com     |
|  2 | queue    |   25 | queue@qq.com |
|  3 | LILI     |   26 | lili@qq.com  |
|  6 | KING     |   24 | 1212@qq.com  |
+----+----------+------+--------------+
4 rows in set (0.00 sec)

起别名

mysql> SELECT username AS user FROM user AS u;
+-------+
| user  |
+-------+
| d     |
| KING  |
| LILI  |
| queue |
+-------+
4 rows in set (0.00 sec)

查询表达式中的顺序可以和原数据表中字段的顺序不一致且SELECT中查询表达式将影响着结果的顺序

5.1 WHERE条件进行查询
mysql> SELECT username FROM user WHERE id=3;
+----------+
| username |
+----------+
| LILI     |
+----------+
1 row in set (0.01 sec)

如果没有找到要查询的结果,返回空

mysql> SELECT * FROM user;
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  1 | d        |   45 | d@qq.com     | this is a test |
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
|  6 | KING     |   24 | 1212@qq.com  | NULL           |
+----+----------+------+--------------+----------------+
4 rows in set (0.00 sec)

mysql> SELECT id, username, age WHERE userDes=NULL;
ERROR 1054 (42S22): Unknown column 'id' in 'field list'
mysql> SELECT id, username, age FROM user WHERE userDes=NULL;
Empty set (0.00 sec)

mysql> SELECT id, username, age FROM user WHERE userDes<=>NULL;
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  6 | KING     |   24 |
+----+----------+------+
1 row in set (0.00 sec)
5.2 检测null值

–检测null值方案1
SELECT id, username, age FROM user WHERE userDes<=>NULL;
–检测null值方案2
SELECT id, username, age FROM user WHERE userDes IS [NOT] NULL;

mysql> SELECT id, username, age FROM user WHERE userDes<=>NULL;
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  6 | KING     |   24 |
+----+----------+------+
1 row in set (0.00 sec)

mysql> SELECT id, username, age FROM user WHERE userDes IS NULL;
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  6 | KING     |   24 |
+----+----------+------+
1 row in set (0.00 sec)
5.3 [NOT]BETWEEN …AND

左右都包含

mysql> SELECT id,username,age FROM user WHERE age BETWEEN 23 AND 26;
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  2 | queue    |   25 |
|  3 | LILI     |   26 |
|  6 | KING     |   24 |
+----+----------+------+
3 rows in set (0.00 sec)
5.4 [NOT] IN()
mysql> SELECT id, username,age FROM user WHERE age IN (23, 24, 25);
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  2 | queue    |   25 |
|  6 | KING     |   24 |
+----+----------+------+
2 rows in set (0.00 sec)

mysql> SELECT id, username,age FROM user WHERE age NOT IN (23, 24, 25);
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  1 | d        |   45 |
|  3 | LILI     |   26 |
+----+----------+------+
2 rows in set (0.00 sec)
5.5 逻辑运算符 AND , OR, NOT
mysql> SELECT id, username,age FROM user WHERE age=25 AND id=2;
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  2 | queue    |   25 |
+----+----------+------+
1 row in set (0.00 sec)
5.6 [NOT] LIKE 模糊查询, 通配符 %, _

% 代表可以匹配任意字符的
_可以匹配一个字符

默认忽略大小写

mysql> SELECT id,username,age FROM user WHERE username LIKE '%i%';
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  3 | LILI     |   26 |
|  6 | KING     |   24 |
+----+----------+------+
2 rows in set (0.00 sec)

mysql> SELECT id,username,age FROM user WHERE username LIKE '%_e%';
+----+----------+------+
| id | username | age  |
+----+----------+------+
|  2 | queue    |   25 |
+----+----------+------+
1 row in set (0.00 sec)
5.7 GROUP BY

把值相同的放到一个组中,最终查询结果只会显示组中的一条记录

mysql> SELECT id,username FROM user GROUP BY userDes;
+----+----------+
| id | username |
+----+----------+
|  1 | d        |
|  6 | KING     |
+----+----------+
2 rows in set (0.01 sec)

分组配合GROUP_CONCAT()查看组中某个字段的详细信息

mysql> SELECT GROUP_CONCAT(username),id FROM user GROUP BY userDes;
+------------------------+----+
| GROUP_CONCAT(username) | id |
+------------------------+----+
| KING                   |  6 |
| d,queue,LILI           |  1 |
+------------------------+----+
2 rows in set (0.04 sec)
5.8 group by 配合聚合函数来使用

COUNT(),
MAX()
MIN()
AVG();

mysql> SELECT count(userDes) FROM user GROUP BY userDes;
ERROR 2006 (HY000): MySQL server has gone away
No connection. Trying to reconnect...
Connection id:    11
Current database: king

+----------------+
| count(userDes) |
+----------------+
|              3 |
|              0 |
+----------------+
2 rows in set (0.04 sec)

如果通过分组,直接查询字段, 仅会显示每个组中的一条信息,分组配合GROUP_CONCAT()查看组中某个字段的详细信息

mysql> SELECT id,username FROM user GROUP BY userDes;
+----+----------+
| id | username |
+----+----------+
|  1 | d        |
|  6 | KING     |
+----+----------+
2 rows in set (0.01 sec)

mysql> SELECT GROUP_CONCAT(username),id FROM user GROUP BY userDes;
+------------------------+----+
| GROUP_CONCAT(username) | id |
+------------------------+----+
| KING                   |  6 |
| d,queue,LILI           |  1 |
+------------------------+----+
2 rows in set (0.04 sec)
5.9 HAVING

用HAVING进行分组条件的指定时,一定要保证分组条件要么为聚合函
么条件中的字段必须出现在当前的SELECT语句中

5.10 ORDER BY 排序

语法:ORDER BY 字段名称 ASC | DESC

mysql> SELECT * FROM user;
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  1 | d        |   45 | d@qq.com     | this is a test |
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
|  6 | KING     |   24 | 1212@qq.com  | NULL           |
+----+----------+------+--------------+----------------+
4 rows in set (0.00 sec)

按照年龄降序

mysql> SELECT * FROM user
    -> ORDER BY age DESC;
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  1 | d        |   45 | d@qq.com     | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  6 | KING     |   24 | 1212@qq.com  | NULL           |
+----+----------+------+--------------+----------------+
4 rows in set (0.00 sec)

按照多个字段排序
语法:
ORDER BY 字段名称 ASC | DESC , 字段名称 ASC | DESC…
按照年龄升序,当年龄相同时,按照id降序

mysql> SELECT * FROM user
    -> ORDER BY age DESC, id DESC;
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  1 | d        |   45 | d@qq.com     | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  7 | ee       |   24 | ee@qq.com    | NULL           |
|  6 | KING     |   24 | 1212@qq.com  | NULL           |
+----+----------+------+--------------+----------------+
5 rows in set (0.00 sec)
5.11 随机打乱的函数

SELECT RAND();# 它每次会产生一个0-1之间的随机数

mysql> SELECT RAND();
+--------------------+
| RAND()             |
+--------------------+
| 0.8787515301990803 |
+--------------------+
1 row in set (0.02 sec)

mysql> SELECT RAND();
+---------------------+
| RAND()              |
+---------------------+
| 0.39015106334365074 |
+---------------------+
1 row in set (0.00 sec)

–实现随机记录
SELECT * FROM user ORDER BY RAND();

mysql> SELECT * FROM user ORDER BY RAND();
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
|  1 | d        |   45 | d@qq.com     | this is a test |
|  6 | KING     |   24 | 1212@qq.com  | NULL           |
|  7 | ee       |   24 | ee@qq.com    | NULL           |
+----+----------+------+--------------+----------------+
5 rows in set (0.01 sec)

mysql> SELECT * FROM user ORDER BY RAND();
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  7 | ee       |   24 | ee@qq.com    | NULL           |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
|  1 | d        |   45 | d@qq.com     | this is a test |
|  6 | KING     |   24 | 1212@qq.com  | NULL           |
+----+----------+------+--------------+----------------+
5 rows in set (0.00 sec)

每次查询的结果都不同

LIMIT 限制结果集显示条数,实现分页效果

–语法1:LIMIT 数字
显示结果集的前几条数据
–语法2:LIMIT offset, row_cour
从offset开始,显示row_cour条记录,offset从0开始

和编号没有关系,和查询结果有关系

mysql> SELECT * FROM user LIMIT 3;
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  1 | d        |   45 | d@qq.com     | this is a test |
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
+----+----------+------+--------------+----------------+
3 rows in set (0.03 sec)

分页查询

mysql> SELECT * FROM user LIMIT 0,3;
+----+----------+------+--------------+----------------+
| id | username | age  | email        | userDes        |
+----+----------+------+--------------+----------------+
|  1 | d        |   45 | d@qq.com     | this is a test |
|  2 | queue    |   25 | queue@qq.com | this is a test |
|  3 | LILI     |   26 | lili@qq.com  | this is a test |
+----+----------+------+--------------+----------------+
3 rows in set (0.00 sec)

mysql> SELECT * FROM user LIMIT 3,3;
+----+----------+------+-------------+---------+
| id | username | age  | email       | userDes |
+----+----------+------+-------------+---------+
|  6 | KING     |   24 | 1212@qq.com | NULL    |
|  7 | ee       |   24 | ee@qq.com   | NULL    |
+----+----------+------+-------------+---------+
2 rows in set (0.00 sec)

注:UPDATE 或DELETE 时LIMIT只支持一个参数的形式