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
- 1-PHP基本概念
PHP 概念:服务器脚本语言 静态网站:不支持交互的网站(html) 动态网站:支持数据交互的网站 实现动态网站的技术 实现技术 网站后缀 ASP .asp PHP .php .NET .aspx J ...
- java根据HashMap中的值将其元素排序
思路:HashMap或Map本身没有排序功能,若要进行较轻松的排序,可利用ArrayList中的sort方法 例子: import java.util.ArrayList; import java.u ...
- linux 根分区扩展
linux根分区扩容 今天网站上传图片出问题了,一开始还以为是程序问题,后来发现原来是服务器存储空间不够,明明有200G的磁盘空间,没理由这么快就用完,查了一下分区情况,原来有两块磁盘,根分区只挂载在 ...
- RMQ问题(线段树算法，ST算法优化)
RMQ (Range Minimum/Maximum Query)问题是指: 对于长度为n的数列A,回答若干询问RMQ(A,i,j)(i,j<=n),返回数列A中下标在[i,j]里的最小(大)值 ...
- 不使用回调函数的ajax请求实现（async和await简化回调函数嵌套）
在常规的服务器端程序设计中, 比如说爬虫程序, 发送http请求的过程会使整个执行过程阻塞,直到http请求响应完成代码才会继续执行, 以php为例子 $url = "http://www. ...
- 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 ...
- Spark技术在京东智能供应链预测的应用
1 背景 前段时间京东公开了面向第二个十二年的战略规划,表示京东将全面走向技术化,大力发展人工智能和机器人自动化技术,将过去传统方式构筑的优势全面升级.京东Y事业部顺势成立,该事业部将以服务泛零售为核 ...
- Unity 3D Framework Designing(7)——IoC工厂理念先行
一谈到 『IoC』,有经验的程序员马上会联想到控制反转,将创建对象的责任反转给工厂.IoC是依赖注入 『DI』 的核心,大名鼎鼎的Spring框架就是一个非常卓越的的控制反转.依赖注入框架.遗憾的是, ...
- 如何用Android Studio查看build.gradle源码
上一篇博客里讲过 build.gradle 里的每一行代码基本都是在调用一个方法,既然是这样,我们就可以用 android studio(下面简称as) 去查看它源码的方法注释说明,这样就可以理解每个 ...
- 我所理解的javascript中函数的作用域和作用域链
本文为原创,转载请注明出处: cnzt 文章:cnzt-p 写在前面 一周木有更新了,今天终于攻克了自行车难关,非常开心,特意来一更~ (那些捂嘴偷笑的人我看到你们了快把嘴闭上我会假装没看 ...