Posted by Dan McCullough on 10/11/05 17:12

Yes I believe that is what Richard was saying about "Trap the INSERT
error", you should get an error back from the database about having a
problem with the insert instead of showing that error you will want to
add some logic that when that error occurs you simply generate another
number.

On 10/11/05, aaronjw@martekbiz.com <aaronjw@martekbiz.com> wrote:
> Hi Richard,
>
> Ok... I do already have a Unique index on the column but this process is
> something that I cannot echo out the error code to the user. The code is
> generated on the fly when an order an is placed so you can see... I can't
> echo out the error to the customer.
>
> Can I do an if statement IF an error is returned to try generatre another
> randon code and keep going until one is available? I can do this all
> intenrally without the customer knowing/seeing anything?
>
> Hope I am making some sense. Not trying to confuse the issue.
>
> Thanks. Appreciate your thoughts.
>
> Aaron
>
> > On Mon, October 10, 2005 3:24 pm, Dan McCullough wrote:
> >> create a function to check if the rndnumber=couponcode row count = 0
> >> if not then redo rndnumber if it does = 0 then insert rndnumber
> >
> > Noooooooooooooooooooooooooooo!
> >
> > You are creating a RACE CONDITION in which ONE user might generate a
> > 'valid' code, and ANOTHER user might generate a 'valid' code AT THE
> > SAME TIME, and then they BOTH get the same coupon code.
> >
> > The probability of this is very very very low, but still NOT zero.
> >
> > And it's the kind of thing that won't show up in testing, but sure as
> > God made little green apples, it WILL happen at the worst possible
> > time after you "go live"
> >
> > The database engine has a *TON* of code in it to avoid this kind of
> > Bad Thing happening.
> >
> > Use it.
> >
> > create a UNIQUE INDEX on the column that needs to be unique.
> >
> > Trap the INSERT error.
> >
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