Hi Paolo, Thank you for your feedback.
Why do you think SQL aggregate syntax (e.g. as outlined at http://www.postgresql.org/docs/9.5/interactive/functions-aggregate.html) is a no-go? Can you explain this in detail? QGIS is much closer to a database then it is to a spreadsheet - in fact for most serious QGIS work you store your data in a SQL database. It was my impression that QGIS tries to maintain expression syntax compatible with SQL wherever possible. I think it would be a good thing. The question is how we can specify grouping. I'd like to see support for the following grouping mechanisms: * whole record set * given grouping field or expression * current selection * grouping based on relations (very important to my employer) - also our initial trigger for funding this work * current set of symbology rules or classes (not so important to me, but maybe useful to some) Andreas On 2016-03-16 08:11, Paolo Cavallini wrote: > Hi Nyall, > > Il 16/03/2016 07:17, Nyall Dawson ha scritto: > >> I'm also torn regarding the best syntax to use for aggregates within >> expressions. I'm unsure if the traditional SQL "group by" clauses >> would be a good fit within the existing QGIS expression syntax (eg >> "sum("some_field") group by "some_other_field"). To me it doesn't fit >> with the existing functional approach that the expressions take. But >> on the other hand, trying to implement this as functions would result >> in some very clumsy expressions: "aggregate('sum', "some_field", >> "some_other_field")" or "sum("some_field", "some_other_field") ". Has >> anyone got any other ideas for syntax which would be a good fit? > > Good news, thanks for sharing. > IMHO having a syntax that is easy to use for the average user is a > crucial point. I think using SQL is a no go. Why not using the > spreadsheet syntax? Not that I find it particularly attractive, but at > least everybody is more or less familiar with it. > All the best.
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