Joins / Nulls / Exporting

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01-19-2016 05:21 PM
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New Contributor

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.

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MVP Frequent Contributor

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

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MVP Frequent Contributor

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

View solution in original post

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MVP Esteemed Contributor

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.

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