Re: Principal of view equality?
Date: Mon, 9 Jun 2008 14:04:01 -0400
Message-ID: <xge3k.7324$mh5.1673_at_nlpi067.nbdc.sbc.com>
"Bob Badour" <bbadour_at_pei.sympatico.ca> wrote in message
news:4846bc21$0$4072$9a566e8b_at_news.aliant.net...
> paul c wrote:
>
> > I was just looking at Codd's RM 2 book again (the rather short chapter
> > on views from acm.org) and it seemed to me that what he wrote took it as
> > essential that a view must always equal the expression that defines the
> > view. If so, does this in effect constitute a kind of indirect
> > constraint on any base relations involved?
>
> No. It does, however, specify constraints on the value of the view.
> Tuples can exist in the base relations that have no effect on the value
> of the view.
I thought that "base relations" were also views. What am I missing? Received on Mon Jun 09 2008 - 20:04:01 CEST