Hi, I have to use *st_area(CastAutomagic(geom)) *instead of *st_area(geom)*, otherwise null column is retourned.
Le jeu. 13 sept. 2018 à 11:45, Bo Victor Thomsen < bo.victor.thom...@gmail.com> a écrit : > 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 < > senhor.n...@gmail.com>: > >> Hi Lee, >> >> Can you try removing the quotation marks around geom? >> >> Best wishes, >> >> Alex Neto >> >> A qui, 13/09/2018, 02:04, Lene Fischer <l...@ign.ku.dk> 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 >>> Qgis-user@lists.osgeo.org >>> 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 >> Qgis-user@lists.osgeo.org >> 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 > Qgis-user@lists.osgeo.org > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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