[PHP] Re: customer ids
blueboy ha scritto:
Hi,
I want to create random customer ids. I have an auto incremented coulumn but
I would rather have a 6-8 digit/letter id randomly generated that can be
used as a unique identifier across 3 tables. Does anyone have a algorithm to
generate such a string and can you give the odds against 2 duplicate stings
being generated?
I know this is a strange ask.
R.
Here's how I do it, for 1 single table though.. you'll have to write
yourself the mod to check on more tables. If you plan to have 10
millions records make sure the maxrand is higher.
When the do loop exits you have a unique id.
function generateID() {
$minrand = 1;
$maxrand = ;
$uniqueid[0] = mt_rand($minrand, $maxrand);
$uniqueid[1] = $uniqueid[0];
return $uniqueid[1];
}
do {
//New ID generation
$newid = generateID();
//Database check
$sqlcheck = SELECT youruniqueidhere FROM yourtablehere WHERE
youruniqueidhere = '.$newid.';
$conn = mysql_connect($db_host, $db_username, $db_password);
mysql_select_db($db_name, $conn);
$rs = mysql_query($sqlcheck, $conn);
$rscount = mysql_num_rows($rs);
} while ($rscount != 0);
Cheers,
Burn
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Re: [PHP] Re: customer ids
Hi Burn,
Wednesday, June 6, 2007, 3:55:21 PM, you wrote:
Here's how I do it, for 1 single table though.. you'll have to write
yourself the mod to check on more tables. If you plan to have 10
millions records make sure the maxrand is higher.
When the do loop exits you have a unique id.
function generateID() {
$minrand = 1;
$maxrand = ;
$uniqueid[0] = mt_rand($minrand, $maxrand);
$uniqueid[1] = $uniqueid[0];
return $uniqueid[1];
}
do {
//New ID generation
$newid = generateID();
//Database check
$sqlcheck = SELECT youruniqueidhere FROM yourtablehere WHERE
youruniqueidhere = '.$newid.';
$conn = mysql_connect($db_host, $db_username, $db_password);
mysql_select_db($db_name, $conn);
$rs = mysql_query($sqlcheck, $conn);
$rscount = mysql_num_rows($rs);
} while ($rscount != 0);
Not that it is likely to occur on a low-traffic site, but the above
approach is a race condition waiting to happen I'm afraid. It will
however almost certainly satisfy the needs of the OP as long as his
site stays off digg / slashdot :)
Cheers,
Rich
--
Zend Certified Engineer
http://www.corephp.co.uk
Never trust a computer you can't throw out of a window
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Re: [PHP] Re: customer ids
Richard Davey ha scritto:
Hi Burn,
Wednesday, June 6, 2007, 3:55:21 PM, you wrote:
Here's how I do it, for 1 single table though.. you'll have to write
yourself the mod to check on more tables. If you plan to have 10
millions records make sure the maxrand is higher.
When the do loop exits you have a unique id.
function generateID() {
$minrand = 1;
$maxrand = ;
$uniqueid[0] = mt_rand($minrand, $maxrand);
$uniqueid[1] = $uniqueid[0];
return $uniqueid[1];
}
do {
//New ID generation
$newid = generateID();
//Database check
$sqlcheck = SELECT youruniqueidhere FROM yourtablehere WHERE
youruniqueidhere = '.$newid.';
$conn = mysql_connect($db_host, $db_username, $db_password);
mysql_select_db($db_name, $conn);
$rs = mysql_query($sqlcheck, $conn);
$rscount = mysql_num_rows($rs);
} while ($rscount != 0);
Not that it is likely to occur on a low-traffic site, but the above
approach is a race condition waiting to happen I'm afraid. It will
however almost certainly satisfy the needs of the OP as long as his
site stays off digg / slashdot :)
Cheers,
Rich
Thanks for pointing it out,
I'm well aware of it, but I use it in a back-end facility managed by a
handfull of administrators, and an expected users base within the
100.000 units. The hit rate is 1:1 Perfectly reasonable with 5
possible concurrent threads running the code :)
Worst thing that can happen is having mysql throw an error while trying
to insert an ID that's already present in the database. It gets more
complicated and unpredictable if the field isn't required to be unique
at database design level.
Wanting to make it perfectly safe the check should include the INSERT
statement and continue looping till it's successful as well.
Cheers!
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Re[2]: [PHP] Re: customer ids
Hi Burn, Wednesday, June 6, 2007, 4:39:05 PM, you wrote: Worst thing that can happen is having mysql throw an error while trying to insert an ID that's already present in the database. It gets more complicated and unpredictable if the field isn't required to be unique at database design level. Wanting to make it perfectly safe the check should include the INSERT statement and continue looping till it's successful as well. Or just wrap the whole thing in a stored procedure / transaction (it's what they were invented for after-all :), tasks like this should be pushed to SQL as much as possible imho. Cheers, Rich -- Zend Certified Engineer http://www.corephp.co.uk Never trust a computer you can't throw out of a window -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
Re: [PHP] Re: customer ids
Richard Davey ha scritto: Hi Burn, Wednesday, June 6, 2007, 4:39:05 PM, you wrote: Worst thing that can happen is having mysql throw an error while trying to insert an ID that's already present in the database. It gets more complicated and unpredictable if the field isn't required to be unique at database design level. Wanting to make it perfectly safe the check should include the INSERT statement and continue looping till it's successful as well. Or just wrap the whole thing in a stored procedure / transaction (it's what they were invented for after-all :), tasks like this should be pushed to SQL as much as possible imho. Cheers, Rich True, true :) -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
