Re: Relation subset operators

On 5 juin, 20:32, paul c <toledobythe..._at_oohay.ac> wrote:
> cim..._at_hotmail.com wrote:
> > On 5 juin, 18:56, paul c <toledobythe..._at_oohay.ac> wrote:
> >> cim..._at_hotmail.com wrote:
> ...
> > Question 8 (the one you mentionned): What are the total sales of
> > salesmen who sold ALL purple cars is a particular case of Question1
> > since all salesmen who sold ALL purple cars are the same than ALL
> > salesmen who have sold AT LEAST one purple car.  ...
>
> I believe, au contraire, that the answer is the same as the total sales
> of each salesman (assuming there never were any purple cars, which would
> be a shame IMO).  See "purple parts" in
>
> http://www.dbdebunk.com/page/page/772076.htm

For the moment, let's keep aggregating out of the equation. First, I want to make sure I understand correctly Question 8. The debunk link provided does not explain under what conditions a salesman, who'd be a part of a set of salesmen who have sold ALL purple cars, would NOT also be a salesman who sold AT LEAST one purple car. I would appreciate if you could give me one example clarifying the previous question ? Received on Fri Jun 05 2009 - 21:25:14 CEST