在Mysql中使用重复值停止自动递增

如何解决在Mysql中使用重复值停止自动递增

我有一个称为注释的表，其中有一个具有唯一键的文本列和一个具有自动递增的优先键id列，如果插入重复的文本会产生错误，但也会增加我的id列。有没有一种方法可以在出现重复值时停止自动递增，并且仅在插入记录时才递增？我已经尝试了innodb_autoinc_lock_mode = 0，但仍然无法正常工作，并且还尝试了插入忽略，但计数器仍然上升。我正在使用Mysql 5.7。 谢谢

解决方法

您可以在/etc/my.cnf中设置 innodb_autoinc_lock_mode 。在这种情况下，它适合您。另请参见https://mariadb.com/kb/en/auto_increment-handling-in-innodb/

将此行添加到mysqld部分的配置中，然后重新启动mysql服务

[mysqld]
innodb_autoinc_lock_mode       = 0

查看已设置的模式

MariaDB [(none)]> show variables like 'innodb_autoinc_lock_mode';
+--------------------------+-------+
| Variable_name            | Value |
+--------------------------+-------+
| innodb_autoinc_lock_mode | 0     |
+--------------------------+-------+
1 row in set (0.00 sec)

样品

MariaDB [bernd]> CREATE TABLE IF NOT EXISTS `docs` (
    ->   `id` int(6) unsigned NOT NULL AUTO_INCREMENT,->   `rev` int(3) unsigned NOT NULL,->   `content` varchar(200) NOT NULL,->   PRIMARY KEY (`id`,`rev`),->   unique KEY (content)
    -> ) DEFAULT CHARSET=utf8;
/*INSERT INTO `docs` Query OK,0 rows affected (0.01 sec)

MariaDB [bernd]> /*INSERT INTO `docs` ( `rev`,`content`) VALUES
   /*>   ( '1','The earth is flat'),/*>   ( '1','One hundred angels can dance on the head of a pin'),/*>   ( '2','The earth is flat and rests on a bull\'s horn'),/*>   ( '3','The earth is like a ball.');*/
MariaDB [bernd]>
MariaDB [bernd]> INSERT IGNORE INTO `docs` ( `rev`,`content`) VALUES
    ->   ('1',->   ('1',->   ('2',->   ('3','X The earth is like a ball.');
  INSQuery OK,4 rows affected,1 warning (0.01 sec)
Records: 5  Duplicates: 1  Warnings: 1

MariaDB [bernd]>   INSERT IGNORE INTO `docs` ( `rev`,`content`) VALUES
    ->   ('5','The earth is flat type');
Query OK,1 row affected (0.00 sec)

MariaDB [bernd]> SELECT * from DOCS ORDER by id;
ERROR 1146 (42S02): Table 'bernd.DOCS' doesn't exist
MariaDB [bernd]> SELECT * from docs ORDER by id;
+----+-----+---------------------------------------------------+
| id | rev | content                                           |
+----+-----+---------------------------------------------------+
|  1 |   1 | The earth is flat                                 |
|  2 |   1 | One hundred angels can dance on the head of a pin |
|  3 |   2 | The earth is flat and rests on a bull's horn      |
|  4 |   3 | X The earth is like a ball.                       |
|  5 |   5 | The earth is flat type                            |
+----+-----+---------------------------------------------------+
5 rows in set (0.00 sec)

MariaDB [bernd]>