[Qgis-developer] have aggregate/window expressions ever been discussed?

Régis Haubourg regis.haubourg at eau-adour-garonne.fr
Wed May 28 09:02:21 PDT 2014

Hugo Mercier wrote
> Le 27/05/2014 15:03, Régis Haubourg a écrit :
>> Hugo Mercier wrote
>>> Or
>>>> calculated fields in view can't be explicitly cast, so QGIS should have
>>>> to
>>>> guess data type based on a data scan (a major unadressed issue of
>>>> sqlite)
>>> Hmmm I wasn't aware of this limitation in SQLITE views :(
>> Yes, SQLITE does dynamic typing, so user or provider has to scan values
>> to
>> guess the right type. 
>> Here is a sqlite topic on that [0]
>> And here my initial post in qgis list [1]
>> [0]
>> http://sqlite.1065341.n5.nabble.com/Computed-columns-in-VIEWs-return-NULL-but-should-be-able-to-be-typed-Any-ideas-td56769.html#a56770
>> [1]
>> http://osgeo-org.1560.x6.nabble.com/Spatialite-can-t-type-fields-of-a-view-td5058436.html
> Hi,
> Still on this topic. I made a few tests with sqlite views.
> Indeed you cannot enforce a particular column type, but :
> * you can convert values with CAST (casting 'foobar' to integer gives
> 0), even if the resulting type is undefined
> * QGIS does not seem to have any particular problem with untyped SQLite
> columns, they will be reported as TEXT (QString) in the layer properties
> * Even if the column is untyped, each value has its own type. So if a
> column results from a CAST, to integer say, then the corresponding
> attribute will be in a QVariant typed as an integer when it is fetched.
> You can then use this value in a QgsExpression or a categorized
> symbology as an integer.
> Am I missing other use cases where not having a column type is a problem ?
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Good news!
I couldn't achieve that with views in QGIS 1.8, all field cast to numeric
were converted in Qstrings. 


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