Re: including limited lines depending on input parameter

On Apr 27, 2007, at 11:10 AM, kvnsmnsn(at)cs(dot)byu(dot)edu wrote:
> Okay, this is me back again regarding those two tables I needed
> to join again, <abc> and <def>. Once these tables are joined together
> the resulting table has two fields of interest, <n> and <p>. There
> can be multiple <p> values for one <n> value. I have an input parame-
> ter <i> that can have three values, 1, 2, or 3+. Based on <i> I need
> to include in the output table either one <p> value for each <n> va-
> lue (as far as I know chosen at random) if one exists, two <p> values
> for each <n> value (again chosen at random) if two exist, or all <p>
> values for each <n> value, respectively.
>
> Does anyone know how I would go about generating such an output
> table?
>
> I have a book _Practical PostgreSQL_ that I thought would help me
> figure out how to do this (since my SQL server is PostgreSQL), but so
> far it has been no use. Any information on this would be greatly ap-
> preciated.

You'll want to use the LIMIT clause, though in the 3+ case you'll
want to have no LIMIT. You should probably wrap all this in a plpgsql
function.
--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)