Re: Principal of view equality?
Date: Mon, 9 Jun 2008 23:40:45 -0400
Message-ID: <2Jm3k.926$LG4.296_at_nlpi065.nbdc.sbc.com>
"Evan Keel" <evankeel_at_sbcglobal.net> wrote in message
news:xge3k.7324$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?
>
A base relation is not a derived relation. Received on Tue Jun 10 2008 - 05:40:45 CEST