Re: constraints in algebra instead of calculus
From: paul c <toledobythesea_at_oohay.ac>
Date: Fri, 15 Jun 2007 15:18:37 GMT
Message-ID: <h5yci.30530$xq1.3113_at_pd7urf1no>
>
> ...
>
>
>
> Butting in, pardon the sloppy notation, isn't this an example?
>
> R:
> A B
> 1 1
> 1 2
> 2 1
>
> R1:
> gB
> {1,2}
>
> R2:
> gB
> {1,2}
> {1}
>
> p
Date: Fri, 15 Jun 2007 15:18:37 GMT
Message-ID: <h5yci.30530$xq1.3113_at_pd7urf1no>
paul c wrote:
> Bob Badour wrote:
>
>> Jan Hidders wrote:
>> ...
>>
>>>
>>> You can simplify that a bit:
>>>
>>> R1 := (R{B}) GROUP {B} AS gB
>>> R2 := (R GROUP {B} AS gB){gB}
>>> constraint: R1=R2
>
> ...
>
>> >> Hi Jan, >> >> That constraint looks like a tautology to me. Can you explain how any >> relation with a B attribute could fail the constraint?
>
>
> Butting in, pardon the sloppy notation, isn't this an example?
>
> R:
> A B
> 1 1
> 1 2
> 2 1
>
> R1:
> gB
> {1,2}
>
> R2:
> gB
> {1,2}
> {1}
>
> p
Oops, please ignore that.
p Received on Fri Jun 15 2007 - 17:18:37 CEST