Re: Transforming 1-1-M Ternary Relationships into Logical

1-1-M = Ternary Relationship (A,B,C)

A can have 1 B and 1 C
B can have Many As and Cs
C can have Many As and Bs

http://groups.google.com.mt/group/comp.databases.theory/tree/browse_frm/thread/33c2956edca34a75/0e88b26bd53dcb2c?rnum=1&hl=en&_done=%2Fgroup%2Fcomp.databases.theory%2Fbrowse_frm%2Fthread%2F33c2956edca34a75%2F0e88b26bd53dcb2c%3Fhl%3Den%26#doc_b95911d131acf57a

Bob Badour wrote:
> miklesw_at_gmail.com wrote:
> > What do you mean by "A pointer that allows to design cardinalities"?
> > I'm not following..
> >
> > Cimode wrote:
> >
> >>You are using an incorrect terminology. You believe a relationship is
> >>a pointer that allows to design cardinalities (it is not). The proper
> >>way for you to deal with the problem you are describing is to do some
> >>serious reading about relational model...Here is the reference...Hope
> >>this helps...
> >>
> >>Introduction to Database Theory by CJ DATE
> >>
> >>
> >>miklesw_at_gmail.com wrote:
> >>
> >>>Most text books state that Ternary relationships are implemented as a
> >>>table with FKs for all the relations.. i was wondering how are 1-1-M
> >>>relationships implemented..
> >>>
> >>>It seems pointless to me... In 1-M binary relationships.. the FK is
> >>>placed on the M end...
> >>>In this case it would make sense to put 2 FKs in the Many end..
> >>>
> >>>What is the proper way of implementing this?
> >>>
> >>>Tnx,
> >>>
> >>>Mike
>
> Hi Mike,
>
> Cimode is a crank. In general, you can safely ignore him; however, his
> pointer to Chris Date is sound.
>
> I suspect the reason you have not received any better responses is
> nobody really has any idea what you are talking about.
>
> If you have any 1-1 relative cardinality between two relations, you can
> reduce that into a single relation, which would seem to leave you with a
> simple 1-M foreign key reference. However, I am not confident that I
> even know what you mean by 1-1-M.
Received on Wed Oct 04 2006 - 18:22:14 CEST