Re: Design question regarding data typing
From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 24 Feb 2006 13:58:41 -0800
Message-ID: <1140818321.463348.195440_at_i40g2000cwc.googlegroups.com>
> I still think we need to know what
> purpose having the label "school" or "bank" will serve. Because as
> soon as you need to have just one additional column from the
> specialized table (i.e. schools or banks) in addition to the building
> data, you will have to write a join -- and that makes your
> building_type column instantly redundant.
Date: 24 Feb 2006 13:58:41 -0800
Message-ID: <1140818321.463348.195440_at_i40g2000cwc.googlegroups.com>
Bob Hairgrove wrote:
>
> I still think we need to know what
> purpose having the label "school" or "bank" will serve. Because as
> soon as you need to have just one additional column from the
> specialized table (i.e. schools or banks) in addition to the building
> data, you will have to write a join -- and that makes your
> building_type column instantly redundant.
Having the subtype marker in the table for the common attributes constraints the entities to only participate in a single subtype.
Marshall Received on Fri Feb 24 2006 - 22:58:41 CET