Re: relational db design question

From: Evan Keel <evankeel_at_sbcglobal.net>
Date: Thu, 8 Feb 2007 19:43:22 -0500
Message-ID: <etPyh.3885$MN.2327@newssvr23.news.prodigy.net>

"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:45cbb667$0$323$e4fe514c_at_news.xs4all.nl...
> Evan Keel wrote:
> > ... You are correct in making Magazine, Book, etc subtypes
> > of Reference, at least at the logical level.
>
> You don't know what the OP wants to accomplish
> with his database. Is it relevant to the users of the
> database to distinguish between types of references?
> It depends on that.
> Can we tell every type of reference in advance?
> SMS, email, usenetposting - how to reference that? NNTP or google?

Yes we can.
>
> > You can implement this in three
> > ways:
> >
> > - one big table allowing nulls
> > - many subtype tables
> > - a supertype/subtype tables with discriminator
> >
> > Google "implementing subtypes".
>
> Or, without complete subtyping, two columns: protocol, locator
>
Received on Thu Feb 08 2007 - 18:43:22 CST