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From:Steven Staples Date:May 28 2010 4:15pm
Subject:RE: Using RAND to get a unique ID that has not been used yet
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If you wanted to use/go that route, then why not select a random limit 1
from that table, and then delete that row?

SELECT `column` FROM `table` ORDER BY RAND() LIMIT 1;


On a side note, I would use the auto-inc field still, and store this number
in another field.

Steven Staples



> -----Original Message-----
> From: Jim Lyons [mailto:jlyons4435@stripped]
> Sent: May 28, 2010 11:49 AM
> To: Andre Matos
> Cc: mysql@stripped
> Subject: Re: Using RAND to get a unique ID that has not been used yet
> 
> If your specs are that specific (IDs must be between 1 and 999999)
> then you could create a 999999-row table with one integer column and
> prefill it with the numbers 1 to 999999 in random order.
> 
> Then you could write a function that would select and return the first
> number in the table, then delete that record so you would not reuse
> it.
> 
> Once you've done the work of sorting 999999 numbers in random order
> (which can be done anywhich way) it's easy and you don't have to loop
> an indeterminant number of times.  You would be looping an increasing
> number of times as you begin to fill up the table.
> 
> Jim
> 
> On Fri, May 28, 2010 at 10:38 AM, Andre Matos <andrematos@stripped>
> wrote:
> > Hi All,
> >
> > I have a table that uses auto_increment to generate the Id automatically
> working fine. However, I need to create a new table where the Id must be a
> number generated randomly, so I cannot use the auto_increment.
> >
> > MySQL has a function RAND. So I could use something like this:
> >
> > SELECT FLOOR(RAND() * COUNT(*)) AS RandId FROM mytable
> >
> > But, let's suppose that the RandId is a number that was already used in
> the table. Then I need to run the SELECT again and again until I find a
> number that hasn't been used.
> >
> > Is there a way to have this SELECT to loop until it finds a number that
> hasn't been used?
> >
> > The RandId must be only numbers and length of 6 (from 1 to 999999). No
> other character is allowed.
> >
> > Thanks for any help!
> >
> > Andre
> >
> > --
> > Andre Matos
> > andrematos@stripped
> >
> >
> >
> >
> >
> > --
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> >
> >
> 
> 
> 
> --
> Jim Lyons
> Web developer / Database administrator
> http://www.weblyons.com
> 
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Thread
Using RAND to get a unique ID that has not been used yetAndre Matos28 May
  • Re: Using RAND to get a unique ID that has not been used yetJim Lyons28 May
    • RE: Using RAND to get a unique ID that has not been used yetSteven Staples28 May
      • Re: Using RAND to get a unique ID that has not been used yetAndre Matos28 May
        • RE: Using RAND to get a unique ID that has not been used yetJerry Schwartz28 May
          • Re: Using RAND to get a unique ID that has not been used yetAndre Matos28 May
    • RE: Using RAND to get a unique ID that has not been used yetJerry Schwartz28 May
  • Re: Using RAND to get a unique ID that has not been used yetPerrin Harkins28 May
  • Re: Using RAND to get a unique ID that has not been used yetKevin \(Gmail\)28 May