mysql表a的数据覆盖到表b mysql表中数据

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davisl 2024-03-11 09:04:12

文章标签 mysql表a的数据覆盖到表b mysql 数据库字段用户名 文章分类 MySQL 数据库

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

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