Re: Which normal form is this violating?
Date: Tue, 7 May 2002 14:37:44 +0200
On Mon, 6 May 2002, D Guntermann wrote:
> A very easy way to confirm that the tables forming the underlying
> relationships and data for user views were "exactly" the same after
> running through some complex pre-processing tasks used to isolate
> and record relationships of the original source data was to compare
> the tables once both systems ran through the processes.
The reason that you had to compare the two tables is because you didn't know whether they represented the same predicate or not. Keep in mind that the database cannot in general know if two tables are logically the same or not.
> I'm not arguing for duplication of data elements, tuples, or
> relations, but I am arguing against the notion that the relational
> model prohibits such states from existing.
No, you're not. :-) You were only trying to show that it might be practical to have two tables that represent the same predicate. If you want to show that the relational does not prohibit this, then you have to point this out with *the* definition of *the* relational model in your hand. Let me know when you find it. :-)
- Jan Hidders