Re: insert different from union?

"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message news:bv3vgm$1mc6$1_at_gazette.almaden.ibm.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news:d_ednSQFv-Lb5ojd4p2dnA_at_golden.net...
> > "Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
> > news:bv3ntf$rqa$1_at_gazette.almaden.ibm.com...
> [sinp]
> > > A possibly more interesting question is, should ON INSERT triggers be
> > fired
> > > when someone does
> > >
> > > A := A union B
> > >
> > > ?
> > >
> > > And then what about on
> > >
> > > A := B
> > >
> > > If A equaled { <1, 1>, <2,2> }
> > > and B equals { <2,1>}
> > >
> > > Should we have two DELETE and one INSERT triggers fire, or one DELETE
> and
> > > one UPDATE. If the latter, which row in A does which trigger fire one?
> > >
> > > If you say, triggers don't fire on assignment, what about if I do
> > >
> > > PRE( ( A{candidate key} intersect B{candidate key} ){} = DUM )
> > > A := A union B
> > >
> > > Why should that not fire triggers when the identical
> > >
> > > INSERT INTO A VALUES B
> > >
> > > would.
> > >
> > > Or would it...
> >
> > If you are trying to make the point that triggered procedures are not
yet
> > well-understood, I agree. The principle of cautious design suggests
> > minimizing their use.
>
> I would be some what stonger and say that triggered procedures (as they
are
> typically understood) are incompatable with the idea that INSERT, UPDATE
and
> DELETE are but shorthands.

>

I think we are saying the same thing. If we are to have triggered procedures, we need to start with assignment as a trigger and work from there. The way SQL works (and possibly tutorial D too) puts the cart before the horse.

If insert is a shorthand for an assignment, it will trigger the procedure.

If we want a procedure to trigger in only certain situations, those situations should not depend on syntax including syntactic short-hands. We might find we apply certain conditions frequently enough to desire syntactic short-hands for declaring them. Received on Tue Jan 27 2004 - 00:01:35 CET