Subject Re: GUID/Random number generation?
Author randallsell
--- In, Dean Harding
<dean.harding@...> wrote:
> randallsell wrote:
> > Hi,
> >
> > I have a requirement to create a unique 7 character string (numbers
> > and letters). In the file-based implementation, we simply extracted
> > the first 7 characters of a GUID. But I see no way to obtain a GUID in
> > PSQL. Surely there is a RANDOM function? But didn't find a reference
> > to such a beast in Helen's Bible.
> >
> > BTW- I can't used a Generator because these values are not internal.
> >
> > So, is there a free library I can obtain to either generate a GUID or
> > a random value?
> Well, certainly the first 7 characters of a GUID are not going to be
> unique, either!!
> When you say the value are not "internal" do you mean that some of the
> values are generated in the database, and so are generated outside the
> database?
> That would be fairly easy to solve with a generator, though: simply
> generate odd numbers inside the database, and even numbers outside the
> database. You can do that with the generator by using an "increment"
of 2.
> Dean.

You are correct - the first 7 are not necesarily unique. The full
algorythem in the file-based app does a loop, until it does generate a
unique entry, or stops after 5 seconds. To date, it has never failed
to come up with something before the 5 second timer expires.

The value created is given to the client - it becomes their password.
And it has to be 7 characters so I don't think that Generators are the
way to go. Their next value is too predictable. And I am trying to
keep the logic whole contained in the DB.

So ignoring GUIDs - as that was a hack anyway, it seems what I need is
a random function. Once I have that I can generate 7 random
alpha-numeric values. then run a query to ensure it is unique, and done.

all that is easy - once I know how to generate a random value.