Re: Principal of view equality?
Date: Wed, 04 Jun 2008 13:00:29 -0300
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. Received on Wed Jun 04 2008 - 11:00:29 CDT