From: Jim Winstead
Date: July 30 2007 2:53am
Subject: Re: multiple current_timestamp
List-Archive: http://lists.mysql.com/internals/34917
Message-Id: <20070730025348.GA24884@trainedmonkey.com>
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On Sun, Jul 29, 2007 at 07:02:19PM -0700, Eric Bergen wrote:
> That's a much better example. It does seem very strange that the
> timestamp functionality isn't more flexible. I suspect there are other
> things wrong in that area too. While playing around with timestamp
> definitions I found that the on update timestamp column still has to
> be listed before any other timestamps.
> 
> I can't find anything in the manual that says the "magic" timestamp
> column still needs to be first like it was in 4.0.

It doesn't.

mysql> create table t1 (a timestamp default 0, b timestamp
    -> on update current_timestamp);
Query OK, 0 rows affected (0.01 sec)
mysql> show create table t1\G
*************************** 1. row ***************************
       Table: t1
Create Table: CREATE TABLE `t1` (
  `a` timestamp NOT NULL default '0000-00-00 00:00:00',
  `b` timestamp NOT NULL default '0000-00-00 00:00:00' on update
CURRENT_TIMESTAMP
) ENGINE=MyISAM DEFAULT CHARSET=latin1

I don't know if there is a strong technical reason for only allowing a
single timestamp field to be automatically set or automatically updated,
or the limitation was just a carry-over from when only the first
timestamp field was auto-set/update. I wouldn't expect anyone at MySQL
to jump at implementing this, but a patch would be looked at. (But since
you can get the same effect with a trigger, it may not have a shot.)

Jim Winstead
MySQL Inc.