在mysql表auto_increment中创建一个ID(在事实之后) [英] make an ID in a mysql table auto_increment (after the fact)

问题描述

我从另一个开发人员那里获得了一个数据库.他没有在任何表上使用auto_incrementers.它们都有主键ID，但是他用代码手动完成了所有的递增操作.

I acquired a database from another developer. He didn't use auto_incrementers on any tables. They all have primary key ID's, but he did all the incrementing manually, in code.

我现在可以把它们变成自动增量器吗?

Can I turn those into Auto_incrementers now?

哇，非常好，非常感谢.我的一张桌子工作顺利.但是在第二张表中，我收到此错误...将.\ DBNAME#sql-6c8_62259c"重命名为.\ DBNAME \ dealer_master_events"的错误

Wow, very nice, thanks a ton. It worked without a hitch on one of my tables. But a second table, i'm getting this error...Error on rename of '.\DBNAME#sql-6c8_62259c' to '.\DBNAME\dealer_master_events'

推荐答案

例如，这是一个具有主键但没有AUTO_INCREMENT的表:

For example, here's a table that has a primary key but is not AUTO_INCREMENT:

mysql> CREATE TABLE foo (
  id INT NOT NULL,
  PRIMARY KEY (id)
);
mysql> INSERT INTO foo VALUES (1), (2), (5);

您可以MODIFY列使用AUTO_INCREMENT选项重新定义它:

You can MODIFY the column to redefine it with the AUTO_INCREMENT option:

mysql> ALTER TABLE foo MODIFY COLUMN id INT NOT NULL AUTO_INCREMENT;

验证这已生效:

mysql> SHOW CREATE TABLE foo;

输出:

CREATE TABLE foo (
  `id` INT(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=6 DEFAULT CHARSET=latin1

请注意，您就地修改了列定义，而无需创建第二列并删除原始列. PRIMARY KEY约束不受影响，您无需在ALTER TABLE语句中提及.

Note that you have modified the column definition in place, without requiring creating a second column and dropping the original column. The PRIMARY KEY constraint is unaffected, and you don't need to mention in in the ALTER TABLE statement.

接下来，您可以测试插入是否生成新值:

Next you can test that an insert generates a new value:

mysql> INSERT INTO foo () VALUES (); -- yes this is legal syntax
mysql> SELECT * FROM foo;

输出:

+----+
| id |
+----+
|  1 | 
|  2 | 
|  5 | 
|  6 | 
+----+
4 rows in set (0.00 sec)

我在Mac OS X的MySQL 5.0.51上对此进行了测试.

I tested this on MySQL 5.0.51 on Mac OS X.

我还用ENGINE=InnoDB和一个依赖表进行了测试.修改id列定义不会中断引用完整性.

I also tested with ENGINE=InnoDB and a dependent table. Modifying the id column definition does not interrupt referential integrity.

要响应您在注释中提到的错误150，可能与外键约束冲突.我道歉，在测试之后，我认为它会起作用.这里有几个链接可能有助于诊断问题:

To respond to the error 150 you mentioned in your comment, it's probably a conflict with the foreign key constraints. My apologies, after I tested it I thought it would work. Here are a couple of links that may help to diagnose the problem:

• 什么mysql错误1025(HY000):重命名"./foo"时出现错误(错误编号:150)是什么意思?
• http://www.simplicidade.org/notes/archives/2008/03/mysql_errno_150.html

• What does mysql error 1025 (HY000): Error on rename of './foo' (errorno: 150) mean?
• http://www.simplicidade.org/notes/archives/2008/03/mysql_errno_150.html

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