RE: [PHP-WIN] Random Code

"These values ARE being stored in a database; however, once this database gets to a million or so rows, it would take a very long time to check it doesn't overlap, wont it?" Well, you **could** make a database of ALL possibilities and delete each possibility as it is used :) Then the program would run faster and faster and you could tell people you've been tweaking the code while it's actually running faster all on its own :) --------------------- John Asendorf - jasendorf@lcounty.com Web Applications Developer http://www.lcounty.com - NEW FEATURES ADDED DAILY! Licking County, Ohio, USA 740-349-3631 The benefit to the government of replacing all $1 Federal Reserve notes with $1 coins would be $522.2 million per year, according to estimates of the General Accouting Office released on April 7, 2000. > -----Original Message----- > From: phobo [mailto:antiphobo@paradise.net.nz] > Sent: Tuesday, January 23, 2001 3:48 PM > To: php-windows@lists.php.net > Subject: Re: [PHP-WIN] Random Code > > > Oops, 36^8 :) > > This value would only have to generated perhaps a few times > an hour, but > should't take more than a second to compute. These values ARE > being stored > in a database; however, once this database gets to a million > or so rows, it > would take a very long time to check it doesn't overlap, wont it? > > I also thought about getting the current date/time stamp and > representing it > as this value. This code is an online-order reference number, > so it could be > something like seconds since midnight: > > 36^4 = 1,679,616 > Seconds in a day (60.60.24) = 86400 > > A really effective way would be to get a subsecond count for > the day; so > that 0000 is midnight, and ZZZZ is the end of the that day. > This means there > are about 19 increments a second, which rules out any possibility of > duplicates, because: > > 1. two other characters could be the id of the user (a > numeric value). 36.36 > is 33696, which is much higher than the intended number of > users on the > system (we invisage no more than a few hundred - by the time > the userbase > gets to 33000, I'll be a millionairre and this can be someone > else's job > hehe) > > 2. the two remaining characters could be a day/year thing. > perhaps the days > since the start of the year 2000. 33696/365 is 92; this > system will not be > used for 92 years! > > Does that sound like quite a good algorythm, or do you have a > much easier, > simpler way? > > Siggy > > > > ----- Original Message ----- > From: "Larry Forrister" <L4@stetson.net> > To: <php-windows@lists.php.net> > Sent: Wednesday, January 24, 2001 7:26 AM > Subject: Re: [PHP-WIN] Random Code > > > > Do you mean W3E4-22ER would be valid? If so there would be 36^8 > > (2,821,109,907,456) possible values. > > > > A truly random generator algorithm cannot guarantee uniqueness. I'm > > guessing what you want is to generate each possible value once in a > > pseudo-random order. Would just apparent randomness suffice? > > > > With what frequency do the values need to be generated? > Once every few > > seconds/minutes or multiple times per second? > > ~~LF > > > > > > Sigurd Magnusson wrote: > > > > > Whats the best way to make a completely random, unique code in the > > > format "ABCD-1234" where each of the 8 characters can be > alphanumerc; > > > 0-9,A-Z... I thought about generating a 36^4 number, > converting to to > > > base '36', and repeating the process. What's a good way > to ensure the > > > code is not repeated, though? > > > > > > Siggy > > > > -- > > PHP Windows Mailing List (http://www.php.net/) > > To unsubscribe, e-mail: php-windows-unsubscribe@lists.php.net > > For additional commands, e-mail: php-windows-help@lists.php.net > > To contact the list administrators, e-mail: > php-list-admin@lists.php.net > > > > > > > -- > PHP Windows Mailing List (http://www.php.net/) > To unsubscribe, e-mail: php-windows-unsubscribe@lists.php.net > For additional commands, e-mail: php-windows-help@lists.php.net > To contact the list administrators, e-mail: > php-list-admin@lists.php.net >