Re: Is this bad design ?
From: Fabian Buettner <green_at_tzi.de>
Date: Thu, 11 Mar 2004 13:04:10 +0100
Message-ID: <405055BA.2020608_at_tzi.de>
Date: Thu, 11 Mar 2004 13:04:10 +0100
Message-ID: <405055BA.2020608_at_tzi.de>
> Suggestion A:
> Splitting the table in two were one table only holds the
> valid mothers and one table holds the non-valid mothers.
No. One table (Mothers) contains all mothers (valid and invalid) with all their attributes. The other table (ValidMothers) contains only the mother_ids of valid mothers. Thus ValidMothers models a *subset* of Mothers. Then, if you want a reference to only valid mothers, you can reference ValidMothers.mother_id instead of Mothers.mother_id.
Fabian Received on Thu Mar 11 2004 - 13:04:10 CET