Re: Fwd: Re: Referencing

Quoting Daryl Richter <daryl(at)brandywine(dot)com>:
> lucas(at)presserv(dot)org wrote:
> > Quoting Daryl Richter <daryl(at)brandywine(dot)com>:
> >> It's hard to say without knowing more precisely what you are trying to
> >> model, but I think this push you in the right direction:
> >>
> > Okay, but references between (output/input) and ACTIVITY tables is 1 to N.
> > OUTPUT/INPUT - 1
> > to
> > ACTIVITY - N.
> > And not N to 1 how the example.
> > Then the reference field need to be on "ACTIVITY (send/buy)" table.
> >
>
> Ahh, ok. In that case I reverse it like so:
>
> -- This table hold everything in common for inputs/outputs
> create table transfer(
> id serial primary key
> );

Yes, I think it was what I wanted.
And how I check if a register in "Transfer" table is only referenciable by ONE
table (OR "output" OR "input")?? Would I create a Trigger like:
CREATE or REPLACE FUNCTION TG_output_check() RETURNS TRIGGER AS
$$
BEGIN
IF exists (select 1 from input where transfer_id=NEW.transfer_id) THEN
Raise Exception 'This activity (transfer) is alread setted to INPUT';
END IF;
RETURN NEW;
END;
$$ language 'plpgsql'; CREATE TRIGGER TG_output_check BEFORE INSERT or UPDATE
on OUTPUT EXECUTE PROCEDURE TG_output_check();
CREATE or REP...--- and the some function to INPUT ---

Or is there another way to check it?

Thank you again.