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I'm using ArcMap and I'm trying to write a script that automates a join and then does some reporting.

I'm not very experienced with joins and I'm running into a problem. When I do a join manually (right clicking the shapefile and specifying the join) it does the join seemingly automatically. However, when I try and do a "Join Field" in ModelBuilder it takes a really long time. Minutes.

Is there a different method of automating a join using python or Model Builder that runs faster?

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3 Answers 3

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If you look at the tool help you'll note that Join Field permanently adds 1 or more fields to the input table.

The tool you probably want is Add Join, which works more like the interactive join command to create a temporary join.

You'll probably want to use Remove Join when you're done though to clean up after yourself.

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In addition to blah238's answer, you should also use the Add Attribute Index geoprocessing tool to create an index for the join. This tool accomplishes the same thing as this prompt:

enter image description here

This will greatly increase performance. Note that some read-only table file types (e.g. CSV) don't support attribute indices, so you'll have to export them to a .dbf file first.

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  • creating an index for the join field in the join table sounds a good idea, but would it also be advised to create an index on the join field of the target layer? @dmahr
    – Theo F
    Commented Nov 14, 2017 at 17:16
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This has been reported to the ArcGIS Ideas forum here: https://geonet.esri.com/ideas/8679

A python script to automate joining the fast way has been provided here: http://www.arcgis.com/home/item.html?id=da1540fb59d84b7cb02627856f65a98d

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  • should be noted this script only works with GDB inputs
    – NULL.Dude
    Commented May 10, 2017 at 12:57
  • I struggled with awesome slow JoinField in my script. The link to the python script is worth a lot. Following the instructions there I reduced overall calculation time to 1/7.
    – EikeMike
    Commented Jan 10, 2018 at 19:38

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