Hi Lauri On Tue, Oct 25, 2011 at 5:49 AM, Lauri Kajan <[email protected]> wrote: > Hi all, > > Giovanni Manghi run to a problem with NULL values in a shapefiles > (earlier post). I tested it but couldn't reproduce the error in 1.7.1. > But I found out some other issues with NULL handling in shapefiles. > > Shapefiles don't support null values at least not in ESRI-world. > Though OGR should support reading and writing null values with > shapefiles. Don't know how but it should.
My understanding is that NULL values in dBase files (accompanying shapefiles) is a sort of extension of original file format and not all software support it. > When I opened a shapefile created by arcgis geoprosessor, qgis somehow > shows all the 0 and '' values as a NULL values. I'm now able to search > a field with IS NULL syntax and qgis returns what is expected. I'm > also able to modify the table and change some values to real zeros. > Now a search finds only 0 values when searched [field] = 0. But when I > save this layer with Save as... to a new shapefile all the NULL values > in numeric fields are converted to 0 and in text field to ''. In the > attribute table '' values in text fields still shows as NULL but when > I try to search only [field] = '' works. All zeros in numeric fields > shows as 0 and not NULL. > > Is there some logic or is this a bug to report? Such inconsistent behavior is worth a bug report, do not forget to attach a test shapefile. Martin _______________________________________________ Qgis-developer mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/qgis-developer
