Hi Martijn,

> Not always. When doing JOINs for example, this won't be
> a join with an indexed table, but with a resultset (from the
> procedure) that's being generated "on the fly". This could get
> slowish.

You are right.
As i understand him, he wants to find out in client if locally created
random number is duplacated, before post.
(to prevent of lot of post attempts)
There is a design problem i think.
With this design, if i were Diego, i will fetch all used numbers into
a huge integer array.( integer[1...99999], about 400KB, no problem)
And try to select random one from this array.(from zero value items)

Regards.
Ali

P.S. Hello to there, i miss Nederland.