Hi, I don't know how updated this is, but maybe https://docs.qgis.org/testing/en/docs/user_manual/managing_data_source/create_layers.html#supported-query-language from the docs could also shed some light.
Harrissou Le jeu. 13 sept. 2018 à 12:43, Luigi Pirelli <[email protected]> a écrit : > I dont' know in deep the detail of virtual layers, as far as I remember a > virtual layer have a spatialite support of the virtualised layer. e.g. has > all spatial operators. Geopackage, per definition ,if no spatialite > extension has been loaded, is a simple container e.g. does not have any > spatial operator => this should explain the mistery! > > Luigi Pirelli > > > ************************************************************************************************** > * LinkedIn: https://www.linkedin.com/in/luigipirelli > * Stackexchange: http://gis.stackexchange.com/users/19667/luigi-pirelli > * GitHub: https://github.com/luipir > * Mastering QGIS 2nd Edition: > * > https://www.packtpub.com/big-data-and-business-intelligence/mastering-qgis-second-edition > * Hire me: http://goo.gl/BYRQKg > > ************************************************************************************************** > > > On Thu, 13 Sep 2018 at 11:45, Bo Victor Thomsen < > [email protected]> wrote: > >> Hi Lene - >> >> I've made a few observations regarding the use of GeoPackage in >> DBManager... >> >> I have a *GeoPackage* based table called "renhold" containing polygons. >> Primary key column is an integer called "fid" and the geometry column is >> called "geom" - It's pretty close to your setup >> >> If I use the *DBManager* with the *GeoPackage *dataprovider and execute >> the following statement: *select fid, st_area (geom) from renhold , *it >> returns a table with 2 columns as expected. However , column nr. 2 contains >> only nulls. However, the statement does not result in an error. The >> function "st_area" simply doesn't return a value besides null. >> >> An now the mystery!! : >> >> If I use the *DBManager* with the *Virtual Layers -> Project layers >> *dataprovider >> and execute the following statement: *select fid, st_area (geometry) >> from renhold , *it returns a table with 2 columns as expected. And >> column nr. 2 do contain the expected area values. Go figure... >> >> NB! The "renhold" layer is visible in the map and named "renhold" >> NBB! In the *Virtual Layers* dataprovider you have to use the standard >> name "geometry" to represent the geometry column - not the real column name >> ("geom" in this case) >> >> Actually I have a reasonable explanation: The 2 different dataproviders >> uses different internal functions to calculate the area. However the >> function used by the GeoPackage Dataprovider doesn't work ! >> >> >> Regards >> Bo Victor Thomsen >> LIFA Denamrk >> >> Den tor. 13. sep. 2018 kl. 09.27 skrev Alexandre Neto < >> [email protected]>: >> >>> Hi Lee, >>> >>> Can you try removing the quotation marks around geom? >>> >>> Best wishes, >>> >>> Alex Neto >>> >>> A qui, 13/09/2018, 02:04, Lene Fischer <[email protected]> escreveu: >>> >>>> Hi, >>>> Trying out a geopackage layer in DBManager asking a simple SQL >>>> statement st_area >>>> But when I try to write a statement like this >>>> >>>> SELECT "vandopland".* , st_area("vandopland"."geom") as areal_m2 >>>> FROM "vandopland" >>>> >>>> "geom" is not found. Suggestions as geomfromexifgpsblob or geomfromfgf >>>> or geomfromwkb . Then I get "an error occured" >>>> >>>> Any suggestions what I might have done wrong. >>>> >>>> Regards from a newbee Geopagkace/DBmanager >>>> >>>> Lene Fischer >>>> >>>> >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> [email protected] >>>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> >>> -- >>> Alexandre Neto >>> --------------------- >>> @AlexNetoGeo >>> http://sigsemgrilhetas.wordpress.com >>> http://gisunchained.wordpress.com >>> _______________________________________________ >>> Qgis-user mailing list >>> [email protected] >>> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >>> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user >> >> >> >> -- >> Med venlig hilsen >> >> Bo Victor Thomsen >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
_______________________________________________ Qgis-user mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
