Why does randomness even enter into the picture? Why not...
user_id char(2)
year int <-- use all four digits, don't create another Y2K
thing...
day int <-- or week
serial int <-- would be reset every day/week or whatever
~~LF
phobo wrote:
> Nah the values are being stored in a transaction log type thing ...
>
> Siggy
>
> ----- Original Message -----
> From: "Asendorf, John" <[EMAIL PROTECTED]>
> To: "phobo" <[EMAIL PROTECTED]>; <[EMAIL PROTECTED]>
> Sent: Wednesday, January 24, 2001 10:00 AM
> Subject: 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 - [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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