Re: another aggregates test case...

It's an error because you're not allowed to project non-grouped expressions without SAMPLE(), or other aggregate.

- Steve

On 2010-06-08, at 15:04, Andy Seaborne wrote:

> I don't see why it needs to be an error - with no aggregation GROUP BY can be considered to be a a partial sort.  Cardinality same as without GROUP BY.  This also happens to be a requirement in some apps - results clustered by key but the same number of rows as without grouping. Sorting can make it so, but sorting is potentially more expensive.
> 	Andy
> On 08/06/2010 2:20 PM, Lee Feigenbaum wrote:
>> I would expect this query to be an error, yes.
>> I'd also be happy to define an aggregate query as any query in which:
>> 1. A GROUP BY clause is present, OR
>> 2. An aggregate is included in the query projection
>> Lee
>> On 6/8/2010 9:07 AM, Axel Polleres wrote:
>>> Student of mine pointed me to a somewhat corner test case:
>>> PREFIX rdf:<>
>>> PREFIX rdfs:<>
>>> PREFIX dcterms:<>
>>> PREFIX foaf:<>
>>> PREFIX mpp:<>
>>> SELECT *
>>> WHERE {
>>> ?project rdf:type foaf:Project ;
>>> rdfs:label ?title .
>>> ?person rdf:type mpp:Person ;
>>> rdfs:label ?personName ;
>>> foaf:currentProject ?project .
>>> }
>>> GROUP BY ?project
>>> Actually, I *think* this should be syntactically invalid, as per:
>>> "In aggregate queries and sub-queries only expressions which have been
>>> used as GROUP BY expressions, or aggregated expressions (i.e.
>>> expressions where all variables appear inside an aggregate) can be
>>> projected."
>>> interestingly, the formulation - strictly speaking - doesn't say what
>>> an aggregate query is, but GROUP BY without aggregtate doesn't make a
>>> lot of sense anyways, except that it should have the same effect as
>>> DISTINCT, right(?), but we still don't want to allow in the presence
>>> of GROUP BY some non-grouped/aggregated things to be projected, I assume.
>>> Axel
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Received on Tuesday, 8 June 2010 15:47:22 UTC