Re: The Practical Benefits of the Relational Model

"Paul Vernon" <paul.vernon_at_ukk.ibmm.comm> wrote in message news:aq6c77$16jo$1_at_sp15at20.hursley.ibm.com...
> "Paul G. Brown" <paul_geoffrey_brown_at_yahoo.com> wrote in message
> news:57da7b56.0211032027.7e218417_at_posting.google.com...
> > I dunno. I guess I don't see a logical difference here.
> >
> > What can be done with 'multiple assignment operators' that cannot be
> > done with explicit transaction boundaries? (Or should I just get with
the
> > program a bit more?)
>
> I'll refer you to Bob's answer.

What I probably should have said, is that I'm not trying to claim that my position: we don't *require* transactions, 'does more' than the traditional position: we do require transactions.

If we have transactions and deferred checking we can just about live without multiple assignment, but without deferred checking (which, as you point out is difficult to implement) then multiple assignment is required anyway (else how to you insert into two relvars with a '1-to-1-or-many' constraint between them?).

Also the logical difference is between a single dbvar assignment statement

    D := de;

and an unknown sequence of possibly overlapping relvar assignment statements with possible pauses in between and either ending in a COMMIT or a ROLLBACK.

Seems like a big difference to me.

Regards
Paul Vernon
Business Intelligence, IBM Global Services Received on Tue Nov 05 2002 - 12:17:16 CET