Re: Proposal: 6NF
From: Sampo Syreeni <decoy_at_iki.fi>
Date: Thu, 5 Oct 2006 16:17:11 +0300
Message-ID: <Pine.SOL.4.62.0610051557450.18113_at_kruuna.helsinki.fi>
Date: Thu, 5 Oct 2006 16:17:11 +0300
Message-ID: <Pine.SOL.4.62.0610051557450.18113_at_kruuna.helsinki.fi>
On 2006-10-05, David Cressey wrote:
> An outer join between two relational tables will, in general, produce
> a table with nullable columns.
I'd add that the same applies if we want the relational model to be closed under arbitrary unions. To me that seems somehow more elementary, and it also ties neatly with inheritance modelling: even if you represent entities of subtypes and supertypes by different relations, sometimes it's handier to work on their union.
-- Sampo Syreeni, aka decoy - mailto:decoy_at_iki.fi, tel:+358-50-5756111 student/math+cs/helsinki university, http://www.iki.fi/~decoy/front openpgp: 050985C2/025E D175 ABE5 027C 9494 EEB0 E090 8BA9 0509 85C2Received on Thu Oct 05 2006 - 15:17:11 CEST