Re: insert different from union?
Date: Tue, 27 Jan 2004 13:23:59 -0500
Message-ID: <GJudnaoYs557MYvdRVn-sA_at_golden.net>
"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message
news:bv67dp$1mhc$1_at_gazette.almaden.ibm.com...
> "Bob Badour" <bbadour_at_golden.net> wrote in message
> news: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...
> [snip]
> > > 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?
>
> I suggest that it would have to take into consideration the candidate keys
> on the affected relvars.
>
> One consideration is whether we would want to enforce that number of old
> rows updated equals the number of new rows updated. E.g.
>
> If R equals { <SSN:1023, Name:"John", Age:65>, <SSN:2345, Name:"Jane",
> Age:55> }
> and has two candidate keys {a}, {b}
> and S equals { <SSN:2345, Name:"John", Age:60 }
>
> Then after
> R := S
>
> would we want to say that two rows *were* updated but only one row *has
> been* updated?
Keys have nothing to do with an update trigger, because an update can alter all of the keys. Received on Tue Jan 27 2004 - 19:23:59 CET