Re: One-To-One Relationships
From: vldm10 <vldm10_at_yahoo.com>
Date: Fri, 30 Nov 2007 21:26:56 -0800 (PST)
Message-ID: <a7ba8444-0ad4-467b-8a13-c6bdefb83bde_at_w40g2000hsb.googlegroups.com>
Date: Fri, 30 Nov 2007 21:26:56 -0800 (PST)
Message-ID: <a7ba8444-0ad4-467b-8a13-c6bdefb83bde_at_w40g2000hsb.googlegroups.com>
On Nov 30, 9:34 am, Jan Hidders <hidd..._at_gmail.com> wrote:
> Why by only one attribute? Why not by a set of attributes? Or a
> combination of attributes and relationships (as is the case for weak
> entities)?
This is OK, but my advice to you -don't use it often.
I will give you one example:
The relation has A1, A2, A3, A4 "attributes" and they are mutually
independent (i.e. they are in BCNF)
The "attributes" can change their values for "entity" like in
"temporal DB". User needs on line all information for any "entity" in
any moment.
Can you please write the key for this relation so that we can discuss
it.
Vl Odrljin Received on Sat Dec 01 2007 - 06:26:56 CET