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Re: abnormal forms

From: paul c <toledobythesea_at_oohay.ac>
Date: Sat, 15 Apr 2006 15:18:44 GMT
Message-ID: <o980g.25403$WI1.2059@pd7tw2no>


x wrote:
> "paul c" <toledobythesea_at_oohay.ac> wrote in message
> news:QHa%f.6021$WI1.5342_at_pd7tw2no...
>
> ...
>

>>For example, (using ttm-style braces and for convenience omitting type
>>names), is a SUPP{S#} relation logically the same value as a SUPP{{S#}}
>>relation that is (somehow) constrained to have only one tuple?  (not to
>>be confused with one that somehow allows multiple tuples).

>
>
> Maybe you should define an abnormal join first. :-)
>
>

Not sure if you were kidding, but as opposed to defining abnormal join, I wonder if it isn't already defined. Regardless, one would have to decide how join could be involved since it must be involved. Just what that would mean is another question. if an sva and an rva in two otherwise different relations have the same name would the join (or <AND>) of the two contain an rva or an sva or both?

if you accept that certain rva's can't be expressed as sva's with the same cardinality there might be times when the decision needn't be made, such as in a constraint expression.

p Received on Sat Apr 15 2006 - 10:18:44 CDT

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