Re: insert different from union?
Date: Tue, 27 Jan 2004 10:28:41 -0500
Message-ID: <M6-dndRhUvJNHovdRVn-uw_at_golden.net>
"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
news:bv5odr$1me2$1_at_gazette.almaden.ibm.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news:erednbkUIcjoAYjdRVn-vA_at_golden.net...
> > "Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
> [snip]
> > > Either have I/U/D as primatives and keep your triggered procedures,
> > > referential actions and row level transitions constraints, or be brave
> and
> > > drop the lot of them. I say drop 'um all, and revel in a clearer
model
> > (and
> > > after some work, a more functional model).
> >
> > I think we are saying the same thing.
>
> Mostly, but again I think I'm being stronger. Rather than saying 'there is
> work to do' to understand these things fully which may or may not result
in
> them being workable, I'm optioning that they *are not* workable.
>> > procedures, we need to start with assignment as a trigger and work from
> > If we are to have triggered
> > there.
>
> Actually, I don't actually think triggered procedures are a good idea at
> all, never mind the obvous difficuties of defining I/U/D triggered
versions.
>
> > The way SQL works (and possibly tutorial D too) puts the cart before
> > the horse.
>
> Agreed for SQL, tutorial D is dangously close in places to assuming that
> there is such a thing in general as a 'row update'.
>
> Going back to my example,
>
> If R equals { <a:1, b:1>, <a2, b2> }
> and has two candidate keys {a} and {b}
> and S equals { <a2, b1>, <a1, b2> }
>
> Then
>
> R := S
>
> Leaves us with a tricky question about which, if any rows got 'updated'.
> I'm not sure that there is any usefull general answer to that question.
>
> Of course I could be wrong, and that some consistent method of identifying
> 'updated rows' would be usefull. But, it all just smacks of row level
> thinking in my opinion.
It would nevertheless trigger an assignment trigger even if it does not trigger an insert, update or delete trigger. The question is: If we are to have an short-hand for a trigger condition called update trigger, what is the condition? Received on Tue Jan 27 2004 - 16:28:41 CET