Re: constraints in algebra instead of calculus

Bob Badour wrote:
> David Cressey wrote:
>

>> "paul c" <toledobythesea_at_oohay.ac> wrote in message
>> news:MtUci.31107$NV3.16822_at_pd7urf2no...
>>
>>> paul c wrote:
>>> ...
>>>
>>>> ...  In other words, when all
>>>> attributes are grouped, the result has the same number of rows as the
>>>> input.
>>>> ...
>>>
>>>
>>> If this is right, what I don't see is how one could GROUP a table with
>>> more more than one row and get a result that had only one row unless
>>> some projection to eliminate an attribute was made after grouping on all
>>> attributes except the one that is subsequently projected away.  Not sure
>>> if that matters though.
>>
>>
>>
>> PMFJI.  I'm not following much of this discussion, but I want to ask the
>> following.
>>
>> If you were to GROUP on no attributes at all,  wouldn't you get a result
>> with only one row?
>> Does "GROUP on no attributes at all"  even make sense?

What I wrote above was wrong-headed, I had the TTM GROUP def'n all balled-up. I guess any time some operation involves sets it makes "sense" to check what happens when all of the set or none of it is specified, whether the result is useful is another thing. Grouping on all attributes seems to have occasional use but at the moment I can't seem much use for grouping on none.

p Received on Tue Jun 19 2007 - 02:52:43 CEST