From: leonard@lf-clark.prestel.co.uk (Leonard F. Clark)
Subject: Re: entity relationship question
Date: 1998/10/10
Message-ID: <361f3958.2379711@news.prestel.co.uk>#1/1
References: <6vdks3$g8t$1@newman.pcisys.net>
Organization: Scotland-On-Line
Newsgroups: comp.databases.oracle.server,comp.databases.oracle.misc


Harold,

I think another (and more physical) way of expressing what sooz says
is:

a) the relationship is valid either way, but
b) it's vital which is the "driving" entity

After all, if you start with ORDER LINE, you *will* end up with a many
to one with ORDER.  However, the questions you can answer *will*
depend on which direction of relationship you're looking at.

Physically, it *is* important: if you are going to constrain a
relationship with a foreign key constraint, you'll need to know which
end depends on which.

Len



On Tue, 6 Oct 1998 11:43:11 -0600, "Harold Gray"
<hgray@stampoutspamcsprings.com> wrote:

>This is a rather trivial question that has bugged me and is mentioned quite
>a bit in certification materials.
>
>I was wondering if someone out there could tell me the difference between a
>one-to-many and a many-to-one relationship concerning entities.  Is it not
>just reflective of the order the entity is described?
>
>Thanks in advance!!
>Harold
>
>