Hello,
How do generate unique serial or order number in php without checking against db?
A:
If you want to guarantee uniqueness then you have to check against something. You could use a flat file and store just the most recently used number (which you can then increment), but it would be silly not to use a database. You need to store a bunch of other information linked to the number (contact details, what the order consists of, etc) and a database is ideal for that.
David Dorward
2010-06-21 05:50:59
if i generate from date string like this date(YmbHis) would it be unique if the site is heavily used
Smith
2010-06-21 05:52:26
No.............
thomasrutter
2010-06-21 05:56:26
^Especially if your server observes DST. I think it's best just to check the DB (or have it generate the order number for you as suggested by Thomas). It's not heavy on the database, and even if it were, you probably aren't generating more than a few dozen order numbers per minute.
Lèse majesté
2010-06-21 06:39:48
A:
If you are using a MySQL database, you can generate a serial order number without needing to pre-check the database by using an auto_increment column. Inserting a new row will cause a new, unique ID to be assigned to that column without having to read/write that column in your PHP.
Alternatively, if you want a globally unique ID without even a database, then you could use PHP's uniqid() function. Note that this returns a string. If you use more than one physical machine or move between servers you should add a prefix (first argument) that is different on every machine. When used on the same machine, this function should never return the same string value twice.
thomasrutter
2010-06-21 05:53:29
@Smith: http://php.net/manual/en/function.mysql-insert-id.php (But not sure if it requeries or not.)
Svish
2010-06-21 08:58:11
I doubt that mysql_insert_id creates a new DB query, given the description (for example, the fact that it's retained for less time than MySQL's LAST_INSERT_ID()). But it is a good question.
thomasrutter
2010-06-22 06:12:56
A:
There are several issues using autoincrement columns in mysql (not least the fact that it does not scale to equivalent nodes).
While you can maintain a sequence generator just about anywhere (memcache, files, database) PHP does not implmenet sophisticated file locking semantics - in addition to affecting performance you can quickly get into deal-lock situations. It doesn't scale to large volumes.
If you've got PL/SQL available, then I'd recommend implementing a sequence generator there - alternatively you might consider implementing a generator in PHP and sqlite.
I would strongly recommend that you implement your generator to create numbers of format:
$use_number = ++$sequence_number . str_pad($node_id, '0', $max_nodes, STR_PAD_LEFT);
Where node_id is a number uniquely referencing the storage substrate where the current sequence number is stored. And $max_nodes is somewhat more than the the max number of digits found in $node_id (e.g. 3 would allow up to 999 nodes).
Alternatively treat it as a string with punctuation between the 2 parts (and/or store the 2 parts in different database columns).
C.
symcbean
2010-06-21 08:40:34