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@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 - 02:15:04 CDT