paul c wrote:
> Jon Heggland wrote:
>> paul c wrote:
>>> (group and ungroup seem to always imply a key, possibly a
>>> different one from the input relvar's key and this seemed a little
>>> chicken and egg to me).
>>
>> I don't understand this.
>
> Maybe I should have said that group always seems to imply an additional
> FD in the result and ungroup always seems to imply the removal of one in
> the result?
Yes, now I see what you mean. Certainly the output of a relational
operation will have different FDs/keys than the input. That is to be
expected---the set of attributes changes, after all---and it goes for
*all* the relational operators, not just group/ungroup. What's
chicken/egg about it?
--
Jon
Received on Fri May 05 2006 - 01:30:48 CDT
