Hi,
I see that I haven't made myself clear. Please take the statement to
create a table below as example.
CREATE TABLE `mytable` (
`id` INT UNSIGNED NOT NULL ,
`description` VARCHAR( 255 ) NOT NULL ,
`date_insert` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ,
`date_update` TIMESTAMP ON UPDATE CURRENT_TIMESTAMP NOT NULL DEFAULT
CURRENT_TIMESTAMP ,
PRIMARY KEY ( `id` )
) ENGINE = MYISAM;
This triggers the error:
#1293 - Incorrect table definition; there can be only one TIMESTAMP
column with CURRENT_TIMESTAMP in DEFAULT or ON UPDATE clause
Let's say this table does not trigger an error and I would do the
following queries:
INSERT INTO `mytable` (`description`) VALUES ("My first item");
UPDATE `mytable` SET `description` = "Changed my first item" WHERE
`id`=1;
The fields would not hold the same data.
At this moment you cannot use 'ON UPDATE CURRENT_TIMESTAMP' if you also
have a field like `date_insert`. Instead you need to create a trigger to
do this behavior.
I hope I managed to make my issue clear with this example.
Best regards,
Arnold
Eric Bergen wrote:
> It makes sense to only allow one field to have current_timestamp
> because having more than one field with current_timestamp would mean
> both columns are storing the same data. Is it really that difficult to
> have date_updated be current_timestamp and date_added set to null in
> the insert query? I don't understand the need for triggers. What
> problem are you trying to solve with code or triggers?
>
>
>
> On 7/28/07, Arnold Daniels <info@stripped> wrote:
>
>> Hi all,
>>
>> Why can there be only one timestamp field with current_timestamp in
>> default or on update?
>>
>> I've been wondered about this for a long time. A table often has a field
>> `date_added`, with the current timestamp only as default, and a field
>> `date_changed` with a changing timestamp upon updating. Basically it is
>> irritating me, since now I have to either solve this in code or use a
>> trigger. Also because I do not understand why this limitation is necessary.
>>
>> Is this something that is subjected to change in MySQL 6? I haven't seen
>> any plans for it.
>>
>> Best regards,
>> Arnold
>>
>> --
>> MySQL Internals Mailing List
>> For list archives: http://lists.mysql.com/internals
>> To unsubscribe: http://lists.mysql.com/internals?unsub=1
>>
>>
>>
>
>
>
