每次更新时，MySQL CURRENT

本文介绍了每次更新时，MySQL CURRENT_TIMESTAMP字段都会更新的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

解释此问题的最佳方法是举一个例子.

The best way to explain this problem is with an example.

CREATE TABLE `example` ( `id` int(11) NOT NULL AUTO_INCREMENT, `data` varchar(255) DEFAULT NULL, `created` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, `updated` datetime DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8

结果:

id | data | created | updated (NULL)| (NULL) | (NULL) | (NULL)

然后我插入一些数据:

INSERT INTO example ( `data` ) VALUES ( 'abc123' )

结果:

id | data | created | updated 1 | abc123 | 2013-01-16 13:12:16 | (NULL)

然后我更新

UPDATE example SET `data` = 'def456', `updated` = NOW() WHERE id = 1

结果:

id | data | created | updated 1 | def456 | 2013-01-16 13:16:24 | 2013-01-16 13:14:26

问题:请注意created字段也是如何更新的，并且正确保存更新后的字段的时间略有不同.我已经在同一数据库上设置了这个示例表和其他示例表，而没有出现此问题，所以我对此完全感到困惑.

The problem: Notice how the created field also updates and has a slightly different time to correctly saved updated field. I have set up this example table and others similarly on the same database without this problem, so I'm completely baffled by it.

推荐答案

这很可能是偶然创建问题表表的方式:

This is likely how the problem table table was accidentally created:

CREATE TABLE `example` ( `id` INT(11) NOT NULL AUTO_INCREMENT, `data` VARCHAR(255) DEFAULT NULL, `created` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP, `updated` DATETIME DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=MYISAM DEFAULT CHARSET=utf8;

也许有人使用了第三方软件来创建它?

Perhaps someone used 3rd party software to create it?

ON UPDATE CURRENT_TIMESTAMP将破坏创建日期.因此，要解决问题，请像这样使用ALTER TABLE:

An ON UPDATE CURRENT_TIMESTAMP is going to destroy the create date. So to solve the problem use ALTER TABLE like so:

ALTER TABLE example CHANGE created created TIMESTAMP DEFAULT CURRENT_TIMESTAMP;

这将消除每次更新时对created字段的不必要覆盖.

This will get rid of the unwanted overwrite of the created field on every update.