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From: Bob Badour <bbadour@pei.sympatico.ca>
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Subject: Re: Foreign superkey support
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Date: Tue, 08 Aug 2006 12:26:40 GMT
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Jon Heggland wrote:
> Bob Badour wrote:
> 
>>It occurs to me a superkey reference implies something less than 3rd
>>normal form because any attributes over and above the irreducible key
>>will be functionally dependent on the foreign key.
> 
> In most cases (but not all) there will be normalisation issues, yes.
> However, the foreign superkey (FSK) will typically control the
> redundancy and prevent anomalies.
> 
>>Why include them in the referencing relation at all?
> 
> Pragmatic reasons. For instance as an alternative to an ASSERTION-type
> join-based constraint, which many(? most? Does anybody know?) DMBSs
> don't support.

I don't follow your reasoning. If you simply omitted the dependent 
attributes from the referencing relation, normal foreign key constraints 
would suffice.