Re: A different definition of MINUS, part 4

From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 09 Jan 2009 07:02:14 -0800
Message-ID: <nEJ9l.9$tD1.6_at_newsfe07.iad>



Bob Badour wrote:
...
>> can be got without Forall, as long as we have projection.  I gather 
>> that 'full relation' often means a cartesian product.

>
> Just a relation expressing all of what all is. In the suppliers/parts
> example, one might group parts from SP into a relation valued attribute
> and then compare that against the P relation projected on {P}
>
> I am unsure of the exact notation but something like:
>
> (SP{S,P} GROUP Parts{P} | Parts = P{P}){S}
>

Excellent! It hadn`t occurred to me to use GROUP this way. Seems to take advantage of the way GROUP always implies a key or fd that might not have been present without GROUP.   Received on Fri Jan 09 2009 - 09:02:14 CST

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