dont forget that md5($anyString) can return two hashes with the same value (if you have a db with 1,000,000 entries using this, it may happen)
best, fernando On Wed, Mar 11, 2009 at 5:12 AM, Artur Marnik <ar...@marnik.net> wrote: > Joey Derrico wrote: > >> One possibility would be to make a DB table with 2 columns. One where each >> row has a value from 00000000 through 99999999, and the other column marked >> as for used. When you need to generate the random number you can query the >> database for each # not currently used and select randomly from the values >> not in use and just update the DB to mark it as used so it won't come up >> again. You won't have repeating numbers then. However it will slow down your >> application because that is a lot of rows to go through. >> >> Joey Derrico >> > > actually query like: > select id, rand_number from rand_numbers where used = '0' limit 1; > and then: > update rand_numbers set used = '1' where id = '$row['id']' > > will be very fast even if table has millions of entries > only generating the numbers will be slow but you have to run it only once > > also make sure to lock the table before and unlock after so you don't have > two users selecting the same entry > > this solution is good only if you know how many random number you will need > another way is to use two tables - prefix and then rand_numbers > prefix has only one entry and you concat it with value selected from second > table > after you run out of random numbers you just have to empty random_numbers > table and regenerate values and change prefix to something else > > but it is all complicated and I will just use old good md5(uniqid(rand(), > true)) if possible > > Artur > > > > > _______________________________________________ > New York PHP User Group Community Talk Mailing List > http://lists.nyphp.org/mailman/listinfo/talk > > http://www.nyphp.org/show_participation.php >
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