Re: About Entity Relation Diagram
From: Mike MacSween <mike.macsween.nospamplease_at_btinternet.com>
Date: Fri, 17 Dec 2004 14:44:09 -0000
Message-ID: <41c2f0c9$0$223$5a6aecb4_at_news.aaisp.net.uk>
Date: Fri, 17 Dec 2004 14:44:09 -0000
Message-ID: <41c2f0c9$0$223$5a6aecb4_at_news.aaisp.net.uk>
"Gene Wirchenko" <genew_at_mail.ocis.net> wrote in message
news:nmd3s0tioi7mscglip37208g0u45g5v3tt_at_4ax.com...
>>I do, however, have another question. What will the primary key of the
>>entity INTERESTS and APPEARANCE be? I read somewhere that when relating 2
>>entities with a relation, the relation doesn't have to include the primary
>>keys of the entities it relates. For example, between member and tape, the
>>relation RENTAL doesn't have to include MemverID and TapeID, only DateRent
>>and DateDue.
>
> This is not correct. You need to have the keys. What you do not
> do is show them when at the logical level. They are implied. (Think
> of how you would use that relation. You need to have the keys.)