Re: atomic
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 05 Nov 2007 23:16:23 -0400
Message-ID: <472fdc8d$0$14839$9a566e8b_at_news.aliant.net>
>> 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.
Date: Mon, 05 Nov 2007 23:16:23 -0400
Message-ID: <472fdc8d$0$14839$9a566e8b_at_news.aliant.net>
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. Received on Tue Nov 06 2007 - 04:16:23 CET