Error "System error: null"" Running Flow Containing MySQL to Flat File Joins

Published: 24 Apr 2018
Last Modified Date: 20 Feb 2019


When running a flow in Tableau Prep Builder that contains joins or unions of MySQL and flat files, the following error message occurs:
"System error: null"

Also, the following error can be found in the Tableau Prep Builder logs:
"Unable to process output step: Failure evaluating to database: ERROR:  collation mismatch, use COLLATE statements to resolve"


Tableau Prep Builder 2019.1.1 and earlier versions


Option 1:

Install Tableau Prep Builder 2019.1.2 or a newer version. Click here for downloads of Tableau Prep: Tableau Prep Downloads and Release Notes. For more information on current releases, see Install Tableau Prep and Prep Upgrade.

Option 2:

Change the collation of the fields used in the join or union in MySQL to "latin1_general_ci".

Option 3:
Convert the flat file to a .hyper and use the .hyper in the flow instead. 


This behavior is related to a known issue with ID 850851 which has been corrected in Tableau Prep Builder 2019.1.2. 
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