Re: foreign key to multiple tables depending on another column's value

On Wed, May 29, 2013 at 9:58 AM, Rodrigo Rosenfeld Rosas <rr(dot)rosas(at)gmail(dot)com
> wrote:

> I know I could use a trigger, or some check constraint maybe, to ensure
> the field exists upon insert (or update), but I can't ensure the database
> will become inconsistent in case I remove a mapped field from the other
> schema.
>
> Now I can finally explain my question: is it possible that I set some sort
> of foreign key whose referenced table and column would depend on the value
> of another column?
>

The FK tests are basically triggers, but highly optimized.

That said, the way they enforce the integrity is by having a trigger on
both tables. So for your custom need here, you would want to put a trigger
on the referenced table to disallow deleting a value that is still
referenced, or do whatever appropriate action upon delete/update your
application needs.