I saw that this conversation took place on this newsgroup last year:
From: Alex Farran <a...@alexfarra n.com>
Date: Mon, 09 Feb 2004 15:16:51 +0000
Subject: Re: MySQL Lock ?[color=blue][color=green]
>> I was under the impression that MySQL has some sort of queue that
>> prevents corruption due to multiple concurrent writes.[/color]
>
> If he does
> SELECT current value;
> INSERT record with value;
> it is possible, if more than one person is using the system, for
> multiple users to read the same current value and so insert the same
> value.
> Without using triggers or subselects I'm not sure how you could do it
> reliably.[/color]
..
..Um, LOCK TABLES?
..
..http://www.mysql.com/doc/en/LOCK_TABLES.html
..
..If you can't do that for some reason, you could always implement your
..own locking mechanism around the PHP that executes the query.
I'm sure a lot of people do this in PHP, and I'd love to hear some
approaches that have been tried, and what works. Is there a concensus
about what the best model is?
From: Alex Farran <a...@alexfarra n.com>
Date: Mon, 09 Feb 2004 15:16:51 +0000
Subject: Re: MySQL Lock ?[color=blue][color=green]
>> I was under the impression that MySQL has some sort of queue that
>> prevents corruption due to multiple concurrent writes.[/color]
>
> If he does
> SELECT current value;
> INSERT record with value;
> it is possible, if more than one person is using the system, for
> multiple users to read the same current value and so insert the same
> value.
> Without using triggers or subselects I'm not sure how you could do it
> reliably.[/color]
..
..Um, LOCK TABLES?
..
..http://www.mysql.com/doc/en/LOCK_TABLES.html
..
..If you can't do that for some reason, you could always implement your
..own locking mechanism around the PHP that executes the query.
I'm sure a lot of people do this in PHP, and I'd love to hear some
approaches that have been tried, and what works. Is there a concensus
about what the best model is?