Re: atomic

From: David BL <davidbl_at_iinet.net.au>
Date: Mon, 05 Nov 2007 23:02:54 -0800
Message-ID: <1194332574.045710.214370_at_i13g2000prf.googlegroups.com>


On Nov 6, 12:16 pm, Bob Badour <bbad..._at_pei.sympatico.ca> wrote:
> paul c wrote:
> > Bob Badour wrote:
>
> >> paul c wrote:
>
> >>> Bob Badour wrote:
>
> >>>> paul c wrote:
>
> >>>>> paul c wrote:
> >>>>> ...
>
> >>>>>> if those make sense, by the D&D definition of "cartesian product",
> >>>>>> I think r1 |x| r2 would be empty and I presume so would I(r1 |x| r2).
>
> >>>>> Sorry, let me take that back, I think I should have said
> >>>>> intersection, not cartesian product.
>
> >>>> The join is empty. The intersection is empty. If one renamed one of
> >>>> the "car" attributes to something else, the join would have 4 rows.
>
> >>> I think it would have 20!
>
> >> r1:
>
> >> Name Car
> >> ----------- ------------
> >> {bill} {car1,car2,car4}
> >> {john,fred} {car3}
>
> >> r2:
>
> >> Car Colour
> >> ---------------- ---------
> >> {car1,car3,car4} {red}
> >> {car2} {green}
>
> >> r1 join ( r2 rename Car as Vehicle ):
>
> >> Name Car Vehicle Colour
> >> ------------- ------------------ ----------------- ---------------
> >> {bill} {car1,car2,car4) {car1,car3,car4} {red}
> >> {bill} {car1,car2,car4) {car2} {green}
> >> {john,fred} {car3} {car1,car3,car4} {red}
> >> {john,fred} {car3} {car2} {green}
>
> >> I count 4 rows.
>
> > Okay, I thought you were using the sources from David B's post about his
> > "I" function which would have 20.
>
> I don't bother reading David's posts. I only see what you excerpt, and
> when I replied to you this time, I was replying to you.- Hide quoted text -
>
> - Show quoted text -

I wish Bob would read my posts; his insights would be valuable. Received on Tue Nov 06 2007 - 08:02:54 CET

Original text of this message