Re: Group by

Eddie McGreal writes: 
"Since there is a sort by expression why not a group by as well?"

I agree with you. Groupby is such a common operation that having a 
user-level syntax feature would be very very useful, both for users 
and for optimizers. There is currently an open issue in the XQuery
document, issue 168, asking for this feature -- we will take
your feedback into account when considering this issue. 

A proposal for adding groupby to the language
have been submitted. An common objection has been
that the specification of the semantics through translation 
to XQuery without groupby is difficult, or that it  requires changes 
to the data model (Jonathan Robie said essentially the first, and 
Michael Kay the second). 
But this is not really an objection to any particular proposal for
the feature, it is more an objection to the reality of what grouping does. 
(each grouping creates a sequence of sequences -- the groups) 

I suggest you join the WG so that we can push for this feature together. 
:-) I also suggest that you encourage other members of the community
to voice their comments on the public drafts -- we need the feedback! 

One question: are you suggesting/asking for a single-level grouping feature, 
or are you looking for a grouping feature that allows 
for nested groupings (let's say within the same FLWOR expression)? 

Thanks,

--
Vasilis Vassalos
http://xquerydemo.enosyssoftware.com/
http://www.enosyssoftware.com/download/index.php