"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 - [EMAIL PROTECTED]
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:[EMAIL PROTECTED]]
> Sent: Tuesday, January 23, 2001 3:48 PM
> To: [EMAIL PROTECTED]
> 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" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> 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
> >
> > --
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>
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