mysql - 将mysql列从INT转换为TIMESTAMP

当我还是你的时候，我觉得用PHP生成时间戳并将它们存储在mysql innodb表的INT列是个好主意。现在，当这个表有数百万条记录并且需要一些基于日期的查询时，是时候将这个列转换为TIMESTAMP。我该怎么做？
现在，我的桌子是这样的：

id (INT) | message (TEXT) | date_sent (INT)
---------------------------------------------
1        | hello?         | 1328287526
2        | how are you?   | 1328287456
3        | shut up        | 1328234234
4        | ok             | 1328678978
5        | are you...     | 1328345324

以下是我提出的将date_sent列转换为TIMESTAMP的查询：

-- creating new column of TIMESTAMP type
ALTER TABLE `pm`
  ADD COLUMN `date_sent2` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP();

-- assigning value from old INT column to it, in hope that it will be recognized as timestamp
UPDATE `pm` SET `date_sent2` = `date_sent`;

-- dropping the old INT column
ALTER TABLE `pm` DROP COLUMN `date_sent`;

-- changing the name of the column
ALTER TABLE `pm` CHANGE `date_sent2` `date_sent` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP();

对我来说一切似乎都是正确的，但是当UPDATEpmSETdate_sent2=date_sent;的时间到来时，我会收到一个警告，时间戳值保持为空：

+---------+------+--------------------------------------------------+
| Level   | Code | Message                                          |
+---------+------+--------------------------------------------------+
| Warning | 1265 | Data truncated for column 'date_sent2' at row 1  |

我做错了什么？有没有办法解决这个问题？

最佳答案

就快到了，使用FROM_UNIXTIME()而不是直接复制值。

-- creating new column of TIMESTAMP type
ALTER TABLE `pm`
  ADD COLUMN `date_sent2` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP();

-- Use FROM_UNIXTIME() to convert from the INT timestamp to a proper datetime type
-- assigning value from old INT column to it, in hope that it will be recognized as timestamp
UPDATE `pm` SET `date_sent2` = FROM_UNIXTIME(`date_sent`);

-- dropping the old INT column
ALTER TABLE `pm` DROP COLUMN `date_sent`;

-- changing the name of the column
ALTER TABLE `pm` CHANGE `date_sent2` `date_sent` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP();