解决 MySQL 分页数据错乱重复
前言
一天，小明很着急地在通讯工具上说：这边线上出现了个奇怪的问题，麻烦 DBA 大大鉴定下，执行语句 select xx from table_name wheere xxx order by 字段A limit offset;，
表数据总共 48 条，分页数量正常，但出现了结果混杂的情况，第一页的数据出现在了第二页上；如果 order by 字段B 就不会出现这个现象，怎么会这样呢！
其实，这个问题很简单，如果你有仔细阅读官档的话。^_^
我们先来看看官档是怎么说的：
If multiple rows have identical values in the ORDER BY columns, the server is free to return those rows in any order, and may do so differently depending on the overall execution plan. In other words, the sort order of those rows is nondeterministic with respect to the nonordered columns.
One factor that affects the execution plan is LIMIT, so an ORDER BY query with and without LIMIT may return rows in different orders.
问题重现
本次实验使用社区版 MySQL 5.6.26（因为小明出现问题的环境就是这个版本O(∩_∩)O~），下面先创建实验环境和初始化测试数据：
root@localhost [(none)]>select @@version;
+------------+
| @@version |
+------------+
| 5.6.26-log |
+------------+
1 row in set (0.00 sec)
root@localhost [(none)]>show variables like "sql_mode";
+---------------+------------------------+
| Variable_name | Value |
+---------------+------------------------+
| sql_mode | NO_ENGINE_SUBSTITUTION |
+---------------+------------------------+
1 row in set (0.00 sec)
root@localhost [(none)]>create database glon_ho;
Query OK, 1 row affected (0.04 sec)
root@localhost [(none)]>use glon_ho
Database changed
root@localhost [glon_ho]>create table glon(
-> id int not null auto_increment primary key,
-> name varchar(20) not null,
-> create_time datetime not null,
-> age tinyint unsigned default 18
-> );
Query OK, 0 rows affected (0.01 sec)
root@localhost [glon_ho]>INSERT INTO `glon` VALUES (1, 'Eason Chan', '2017-05-02 08:10:10', 19),(2, 'Glon Ho', '2017-05-03 12:10:10', 18),(3, '赵敏', '2017-05-03 14:10:10', 17),(4, 'Jacky Cheung', '2017-05-02 14:00:00', 22),(5, '周芷若', '2017-05-02 14:00:00', 16),(6, 'Andy Lau', '2017-05-02 14:00:00', 50),(7, '至尊宝', '2017-05-02 14:00:00', 20),(8, '刘三姐', '2017-05-02 14:00:00', 19);
Query OK, 8 rows affected (0.01 sec)
Records: 8 Duplicates: 0 Warnings: 0
root@localhost [glon_ho]>select * from glon;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
+----+--------------+---------------------+------+
8 rows in set (0.00 sec)
这里创建了一个 glon 表，字段有自增 id, 姓名 name, 年龄 age, 及用户注册时间 create_time。
接着来复现问题：
- 根据用户注册时间 create_time 来排序：
root@localhost [glon_ho]>select * from glon ORDER BY create_time limit 0, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
可以看到两次查询结果中都出现了 id 为 8 的刘三姐，从上面初始化数据来看，总共有 8 条数据，现在不但分页出现重复数据，还丢了一条！
问题确实重现了，不过先不急，我们再来试多几组其他的排序方式。
- create_time 和 age 组合排序
root@localhost [glon_ho]>select * from glon ORDER BY create_time,age limit 0, 4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,age limit 4, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
- create_time 和 id 组合排序
root@localhost [glon_ho]>select * from glon ORDER BY create_time,id limit 0, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,id limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
- 主键 id 排序
root@localhost [glon_ho]>select * from glon ORDER BY id limit 0, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY id limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
看到，后面的几组排序方式都没有再出现问题了，结合官档，我们知道 order by 排序的时候，如果排序字段中有多行相同的列值，则排序结果是不确定的。所以后面的几组组合形式的排序或者是主键 id 的排序，因为唯一性高，所以排序是确定的，不会出现结果混乱的问题。
那是不是可以就此结束了呢，no way， 我们再来看下面的实验，继续巩固一下：
- 根据年龄 age 来排序：
root@localhost [glon_ho]>select * from glon ORDER BY age limit 0, 4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY age limit 4, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
咦，这个排序也只是根据一个字段 age 来排序，怎么就没有出问题呢？不急，还有招：
root@localhost [glon_ho]>insert into glon values (9,'乔峰','2017-05-03 13:10:10',22),(10,'段誉','2017-05-03 15:10:10',19),(11,'郭靖','2017-05-03 17:10:10',20),(12,'黄蓉','2017-05-03 08:10:10',19);
Query OK, 4 rows affected (0.01 sec)
Records: 4 Duplicates: 0 Warnings: 0
root@localhost [glon_ho]>select * from glon;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 11 | 郭靖 | 2017-05-03 17:10:10 | 20 |
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
+----+--------------+---------------------+------+
12 rows in set (0.00 sec)
我又给 glon 表新增了几条数据，然后再来看看：
root@localhost [glon_ho]>select * from glon ORDER BY create_time limit 0, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time limit 8, 4;
+----+--------+---------------------+------+
| id | name | create_time | age |
+----+--------+---------------------+------+
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 11 | 郭靖 | 2017-05-03 17:10:10 | 20 |
+----+--------+---------------------+------+
4 rows in set (0.00 sec)
根据 create_time 排序，没有问题了，再来：
root@localhost [glon_ho]>select * from glon ORDER BY age limit 0, 4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY age limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY age limit 8, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
可以看到根据年龄 age 排序，问题出现了。
然后在看看组合的排序：
root@localhost [glon_ho]>select * from glon ORDER BY create_time,id limit 0, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,id limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,id limit 8, 4;
+----+--------+---------------------+------+
| id | name | create_time | age |
+----+--------+---------------------+------+
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 11 | 郭靖 | 2017-05-03 17:10:10 | 20 |
+----+--------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,age limit 0, 4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,age limit 4, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY create_time,age limit 8, 4;
+----+--------+---------------------+------+
| id | name | create_time | age |
+----+--------+---------------------+------+
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 11 | 郭靖 | 2017-05-03 17:10:10 | 20 |
+----+--------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY age,id limit 0, 4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY age,id limit 4, 4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon ORDER BY age,id limit 8, 4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 11 | 郭靖 | 2017-05-03 17:10:10 | 20 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
思考
既然排序不定，那么给排序字段加上索引会不会有用呢？
root@localhost [glon_ho]>alter table glon add index ix_age(age);
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
root@localhost [glon_ho]>show create table glon\G
*************************** 1. row ***************************
Table: glon
Create Table: CREATE TABLE `glon` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`create_time` datetime NOT NULL,
`age` tinyint(3) unsigned DEFAULT '18',
PRIMARY KEY (`id`),
KEY `ix_age` (`age`)
) ENGINE=InnoDB AUTO_INCREMENT=13 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)
root@localhost [glon_ho]>select * from glon order by age limit 0,4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon order by age limit 4,4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from glon order by age limit 8,4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
也可以不在 order by 后面加多一列增加唯一性，可以改写成下面的形式：
root@localhost [glon_ho]>select * from (select distinct g.* from glon g order by age) t limit 0,4;
+----+------------+---------------------+------+
| id | name | create_time | age |
+----+------------+---------------------+------+
| 5 | 周芷若 | 2017-05-02 14:00:00 | 16 |
| 3 | 赵敏 | 2017-05-03 14:10:10 | 17 |
| 2 | Glon Ho | 2017-05-03 12:10:10 | 18 |
| 1 | Eason Chan | 2017-05-02 08:10:10 | 19 |
+----+------------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from (select distinct g.* from glon g order by age) t limit 4,4;
+----+-----------+---------------------+------+
| id | name | create_time | age |
+----+-----------+---------------------+------+
| 10 | 段誉 | 2017-05-03 15:10:10 | 19 |
| 8 | 刘三姐 | 2017-05-02 14:00:00 | 19 |
| 12 | 黄蓉 | 2017-05-03 08:10:10 | 19 |
| 11 | 郭靖 | 2017-05-03 17:10:10 | 20 |
+----+-----------+---------------------+------+
4 rows in set (0.00 sec)
root@localhost [glon_ho]>select * from (select distinct g.* from glon g order by age) t limit 8,4;
+----+--------------+---------------------+------+
| id | name | create_time | age |
+----+--------------+---------------------+------+
| 7 | 至尊宝 | 2017-05-02 14:00:00 | 20 |
| 9 | 乔峰 | 2017-05-03 13:10:10 | 22 |
| 4 | Jacky Cheung | 2017-05-02 14:00:00 | 22 |
| 6 | Andy Lau | 2017-05-02 14:00:00 | 50 |
+----+--------------+---------------------+------+
4 rows in set (0.00 sec)
总之，如果发生了，最简单的方法就是在排序列（如 create time）上加索引，然后在 order by 上明示 primary key，这个问题就非常圆满的解决了。
总结
MySQL 使用 limit 进行分页时，可能会出现重复数据，通过加入 order by 子句可以解决，但是需要注意的是，如果排序字段有相同值的情况下，由于排序字段数据重复,可能会导致每次查询排序后结果顺序不同，分页还是会出现重复数据，这时可以加入第二个排序字段，提高排序的唯一性，最好保证排序的字段在表中的值是唯一的，这样就可以少写一个排序字段，增加查询效率，因为 order by 后面有多个排序字段时，无法用到索引。
推荐 2015年 06 月《数据库内核月报》的一篇旧文：MySQL · 答疑解惑 · MySQL Sort 分页
解决 MySQL 分页数据错乱重复的更多相关文章
- MySQL 分页数据错乱重复
select xx from table_name wheere xxx order by 字段A limit offset;, 表数据总共 48 条,分页数量正常,但出现了结果混杂的情况,第一页的数 ...
- mysql 分页数据错乱
最近在使用mysql 分页查询数据的时候发现返回的数据与预期的不一样,显示数据重复错乱. 在官方文档 有这样一句话 If multiple rows have identical values in ...
- EF获取多个数据集以及MySQL分页数据查询优化
背景:MySQL分页查询语句为 ,10; 一般页面还会获取总条数,这时候还需要一条查询总条数语句 , 这样数据库需要执行两次查询操作.MySQL提供了SQL_CALC_FOUND_ROWS追踪总条数的 ...
- Mysql 删除数据表重复行
准备示例数据 以下sql创建表,并将示例数据插入到用于演示的contacts表中. CREATE TABLE contacts ( id INT PRIMARY KEY AUTO_INCREMENT, ...
- php 解决MySQL插入数据出现 Incorrect string value: '\xF0\x9F\x92\x8BTi...'错误
在项目中向MySQL插入数据时.发现数据插入不完整,通过调试,发现插入语句也没什么特殊的错误. 可是就是差不进去,于是就打开mysqli错误的调试 $ret = mysqli_query($this- ...
- SpringMVC+Mybatis实现的Mysql分页数据查询
周末这天手痒,正好没事干,想着写一个分页的例子出来给大家分享一下. 这个案例分前端和后台两部分,前端使用面向对象的方式写的,里面用到了一些回调函数和事件代理,有兴趣的朋友可以研究一下.后台的实现技术是 ...
- 解决mysql插入数据时出现Incorrect string value: '\xF0\x9F...' for column 'name' at row 1的异常
这个问题,原因是UTF-8编码有可能是两个.三个.四个字节.Emoji表情或者某些特殊字符是4个字节,而MySQL的utf8编码最多3个字节,所以数据插不进去. 我的解决方案是这样的 1.在mysql ...
- 解决mysql导入数据量很大导致失败及查找my.ini 位置（my.ini）在哪
数据库数据量很大的数据库导入到本地时,会等很久,然而等很久之后还是显示失败: 这是就要看看自己本地的没mysql是否设置了超时等待,如果报相关time_out这些,可以把mysql.ini尾部添加ma ...
- 解决mysql插入数据l出现"the table is full"的问题
需要修改Mysql的配置文件my.ini,在[mysqld]下添加/修改两行:tmp_table_size = 256Mmax_heap_table_size = 256M
随机推荐
- gitignore文件中添加新过滤文件，但是此文件已经提交，如何解决？
gitignore文件中添加新过滤文件,但是此文件已经提交到远程库,如何解决? 第一步,为避免冲突需要先同步下远程仓库 git pull 第二步,在本地项目目录下删除缓存 git rm -r --ca ...
- JS中的普通函数和箭头函数
最近被问到了一个问题: >javaScript 中的箭头函数 (=>) 和普通函数 (function) 有什么区别? 我当时想的就是:这个问题很简单啊~(flag),然后做出了错误的回答 ...
- shell脚本监控目录下文件被篡改时报警
思路: 目录下文件被篡改的几种可能: 1.被修改 2.被删除 3.新增文件 md5命令详解 参数: -b 以二进制模式读入文件内容 -t 以文本模式读入文件内容 -c 根据已生成的md5值,对现存文件 ...
- java入门了解02
1:JDK,JRE,JVM的作用关系 (一)作用 JVM:提供java跨平台 JRE:java运行环境 JDK:java开发环境 ...
- centOS下调整swap
[root@localhost /]# mkdir swap [root@localhost /]# cd swap [root@localhost swap]# dd if=/dev/zero of ...
- AndroidAnnotations框架简单使用方法
当我们配置好了框架后,那么久可以来使用了.使用教程网上一大堆,官方也有提供!!!可自行学习深造.下面我简单的贴出几个常用的方法,作为HelloWorld入门: @EActivity(R.layout. ...
- es suggest did you mean资料
term suggester 功能介绍 term suggester 根据提供的文档提供搜索关键词的建议,也就是关键词自动纠错.该链接介绍如何使用 term suggester 语法.term sug ...
- salesforce 零基础学习（六十八）http callout test class写法
此篇可以参考: https://developer.salesforce.com/docs/atlas.en-us.apexcode.meta/apexcode/apex_classes_restfu ...
- linux从入门到精通学习-NFS
NFS网络文件系统 功能 nfs[network file system] 网络文件系统 是FreBSD系统支持的一种系统,允许在网络 上与其它人共享使用文件或文件夹 采用C/S模式 端口号 在vim ...
- 不可不知的 Android strings.xml 那些事
相信 strings.xml 已经是大家在 Android 开发中最熟悉的文件之一了,但其实它也有很多需要注意的地方和一些小技巧,知道了这些可以让你的 Android 应用更加规范易用,大家来看看吧. ...