topic Re: Joins / Nulls / Exporting in Data Management Questions

Joins / Nulls / Exporting

MichaelWebb1 — Wed, 20 Jan 2016 01:21:25 GMT

Hello! I'm trying to join a data file to a shapefile (Census tracts), and then export the result for additional analyses. Some tracts have no/excluded data (too few observations). When I join the files, these appear as <Null> in the shapefile's attribute table, but after exporting, they revert to 0s (their columns contain numerical values). Any way to maintain their <Null> status following export? It's a substantial number of columns, so a batch way to do this would be preferred.

Re: Joins / Nulls / Exporting

ChrisDonohue__GISP — Wed, 20 Jan 2016 02:15:18 GMT

On export Shapefiles will convert NULLS to zeros in many cases - this is expected behavior.

ArcGIS Desktop Help 9.3 - Geoprocessing considerations for shapefile output

One suggestion would be to recalculate all your NULL values before exporting to something obviously different than zero, say -999. Then you will be able to recognize the NULLs after export.

Another suggestion would be to import the shapefile into a geodatabase, do the Join, then export from the geodatabase.

Chris Donohue, GISP

Re: Joins / Nulls / Exporting

JoshuaBixby — Wed, 20 Jan 2016 03:31:23 GMT

Chris Donohue, GISP already provided a fine answer, you should mark it correct. If shape files are the root of your problem, I can't help but think the most straightforward solution is to not use them in the first place.