Re: 1 foreign key to 2 different tables?

Thanks for your input. Yes, there is a lot more to this part of the schema.
The current stucture makes the most sense to us so far, after lots of
thinking. If you are interested I can offer you more details about the
structure, but for now I am looking for how to implement this type of
constraint with a trigger or another method - if there is a better way.

-Ryan Riehle
http://www.buildways.com

-----Original Message-----
From: pgsql-general-owner(at)postgresql(dot)org
[mailto:pgsql-general-owner(at)postgresql(dot)org] On Behalf Of Bruno Wolff III
Sent: Saturday, May 01, 2004 9:40 PM
To: Ryan Riehle
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: [GENERAL] 1 foreign key to 2 different tables?

On Sat, May 01, 2004 at 18:09:34 -0400,
Ryan Riehle <rkr(at)buildways(dot)com> wrote:
> For what I am reading now it looks like this is an opportunity to use
> CREATE ASSERTION, but this functionality appears to be unstable so far and
is not
> recommended for production environments. Is this correct? Otherwise,
can
> someone post an example of implementing a check constraint or trigger
> since I have not created a check onstraint that is above common
> complexity and and have never tried a trigger.

The simplest way to do this is probably be to use two separate fields to
make the references and make sure exactly one of them is nonnull. You also
might want to rethink your design. That you want to do this suggests that
there is something odd about the schema design you have come up with.

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