Re: one to many

> Stephan Szabo wrote:
>
> >On Sun, 16 May 2004, Dennis Gearon wrote:
> >
> >
> >
> >>CC me please.
> >>
> >>How do I set up a one to many relationship in Postgres, (any DB for that
> >>matter.)
> >>
> >>I.E., if a delete or update of a child table causes a row in the parent
> >>table to no longer refer to any rows in the child table, to either cause
> >>Postgres to error out or delete the parent? I can see it does it for
> >>when a parent is upudated or deleted.
> >>
> >>
> >
> >I don't think there's any built in direct way to do this right now, but
> >you could probably build triggers that would do it for you (the current
> >foreign key triggers might give a starting point. You'd probably also
> >want to use CREATE CONSTRAINT TRIGGER to be able to defer the trigger
> >(similarly to how the foreign key deferred works).
> >
> >
> >
> >
> I didn't know you could set up triggers to be deferred! AWESOME! That
> makes for some additional flexibility that I could use.
>
> Thank you very much Stephen. I was beginnning to consider TRIGGERS as
> the solution; Now I know that they will work.

Well, I should note that AFAIK CREATE CONSTRAINT TRIGGER is considered an
"internal" feature. It's unlikely to go away until it's considered okay
to break compatibility with 7.0/7.1 dumps however (and would be more
likely to be replaced with a more general feature anyway).