[Qgis-developer] Aggregates within expression engine

Bernhard Ströbl bernhard.stroebl at jena.de
Wed Mar 16 00:56:20 PDT 2016

just my 2 ct:
I agree with Paolo that normal users do not know SQL, on the other hand 
there might be users that do not know spreadsheet syntax either (e.g. me 
:) which spreadsheet BTW: Excel? LO? or do they use the same syntax? SQL 
would be a standardized approach (and is the syntax already used in QGIS 
expressions). On the other hand if it is possible to "click together" 
the expression it doesn't matter which syntax is used, good 
documentation and direct help is a must here. If you e.g. choose a SUM 
function a GROUP BY woould be added automatically at the end (if not 
already there)
SQL is used at so many places in QGIS: layer filters, labelling, 
rule-based renderer... I would not mix this with different syntax.


Am 16.03.2016 um 08:36 schrieb Paolo Cavallini:
> Il 16/03/2016 08:30, Neumann, Andreas ha scritto:
>> 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.
> Hi Andreas,
> based on my lengthy experience with courses, I'm pretty sure SQL
> commands are out of reach for most "normal" GIS users.
> It is fine to have access to SQL for power users, but aggregate
> functions should IMHO be available to anyone.
> All the best.

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