This is how sql works.You want to apply a function to one column, and the column you are comparing must have a value. Consider this: tag_service != 'xxx' or null != 'xxx'. Null can't be equal or unequal to any value. Even null = null or null != null returns false
hth marco _______________________________________________ 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