Re: Lucid statement of the MV vs RM position?
From: x <x_at_not-exists.org>
Date: Tue, 9 May 2006 10:15:04 +0300
Message-ID: <e3pfed$3ce$1_at_emma.aioe.org>
1
2
S(A)
1
3
1
2
3
Date: Tue, 9 May 2006 10:15:04 +0300
Message-ID: <e3pfed$3ce$1_at_emma.aioe.org>
"Jon Heggland" <jon.heggland_at_idi.ntnu.no> wrote in message
news:e3mnk1$s6u$1_at_orkan.itea.ntnu.no...
> Marshall Spight wrote:
> > Jon Heggland wrote:
> > One the one hand, we have "iterated union." On the other hand,
> > we have "shorthand for a particular extension/projection", which
> > is not very specific, but *could* be a description of what we have
> > in the first case.
> Can you perform a union between two relations by first extending and
> then projecting one relation?
R(A)
1
2
S(A)
1
3
T(A,A)
1,1 1,3 2,1 2,3
U(A)
1
2
3
;-) Received on Tue May 09 2006 - 09:15:04 CEST