Re: Transforming 1-1-M Ternary Relationships into Logical
Date: Wed, 04 Oct 2006 17:25:49 GMT
Message-ID: <x8SUg.250$cz.2955_at_ursa-nb00s0.nbnet.nb.ca>
miklesw_at_gmail.com wrote:
Thus A has two foreign key references: 1 to B and 1 to C.
> B can have Many As and Cs
The question then becomes: Other than a shared A reference, which is
already captured by the two foreign key references to B and C above, how
are B and C related?
Are you talking about A=child, B=mother, C=father? In this case, A has
two binary relationships: the maternal relationship and the paternal
relationship.
> 1-1-M = Ternary Relationship (A,B,C)
>
> A can have 1 B and 1 C
> C can have Many As and Bs
> 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 - 19:25:49 CEST