Re: object algebra
From: Neo <neo55592_at_hotmail.com>
Date: 23 Feb 2004 14:36:14 -0800
Message-ID: <4b45d3ad.0402231436.5674aabe_at_posting.google.com>
Date: 23 Feb 2004 14:36:14 -0800
Message-ID: <4b45d3ad.0402231436.5674aabe_at_posting.google.com>
> > RDM isn't fully general. If it is, why does it need NULLs?
>
> It is fully general, and it doesn't need nulls.
According to Date "Codd now regards NULLs as an integral part of relational model". Codd is correct that NULLs are required in RDM, unless all your data fits neatly in rectangular tables which is not the general case, or unless one resorts to unpractical methods such as generic modelling (ie all data in one table with one column). Received on Mon Feb 23 2004 - 23:36:14 CET