Error "Unable to change the join clause information for <file name>" When Adding Calculated Join Clause to Union Tables

Published: 01 Aug 2017
Last Modified Date: 16 Mar 2020


After adding a join clause using join calculation to a union of tables, the following error might occur

"Unable to change the join clause information for <file name>. Unable to update relation" 


  • Tableau Desktop 10.3.1
  • Text Files
  • Excel


The order of operation to join data connections and also union tables needs to follow these steps:
  1. Drag the first .csv (or .xlsx) file to the Data pane.
  2. Drag the second .csv (or .xlsx) file that you wish to join. 
  3. Then create the Join Calculation
    • In the attached example workbook Union Solution.twbx, the join calculation clause is "K" and the associated join is "Key". 
  4. Finally, drag the last table beneath the first table in the "Drag table to union" field.
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