On Sep 11, 2009, at 3:50 AM, Ashley Sheridan
<ash@xxxxxxxxxxxxxxxxxxxx> wrote:
On Fri, 2009-09-11 at 00:19 -0400, Phpster wrote:
Note that this approach has risks around race conditions. Anytime you
have a construct for the id you run the risk of having it create
duplicate ids. You will need to handle that.
Bastien
Sent from my iPod
On Sep 10, 2009, at 6:49 PM, Ben Dunlap <bdunlap@xxxxxxxxxxxxxxxxxx>
wrote:
I assume that I can get increment value/sequence from db (I used
harcoded
increment value in the code above (generate_id(1))),
but I don't know how I can get this incremental value from db.I use
mysql
5.0.
If you're thinking of retrieving the newest value of an
AUTO_INCREMENT
column, immediately after inserting a row, there are different
ways to
do this depending on how you're connecting to MySQL.
PDO, for example, has a method called lastInsertId():
http://us2.php.net/manual/en/pdo.lastinsertid.php
And the mysql_* family of functions has mysql_insert_id(), etc.
Ben
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Not if you use the functions built specifically for that, i.e. the
ones
that Ben mentioned. In no circumstances should you ever do a "SELECT
MAX(id) FROM table". I've seen this done so many times by people who
should know better, and they even saw no problems when they ran tests
(that was, they tested the systems themselves, and only themselves)
but
then it all fell down as soon as multiple users tried to use it.
Thanks,
Ash
http://www.ashleysheridan.co.uk
I totally agree. Ufortunately, my boss would not agree and the one app
I have to support is full of race conditions. I told them from the
beginning that it would not work and under any load ( btw the max app
load is about 40 people on a server, don't ask, it would make me sad)
we get errors in the app. I get to spend a few hours a week fixing
this crap!
I did just want to point out that there is risk in not using auto
numbers or other unique id mechanisms if you don't pay attention.
Bastien
Sent from my iPod
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