Unable to Change a Field Data Type When Tableau Prep is Connected to a Text File data source

Published: 30 Jul 2018
Last Modified Date: 15 Jul 2019


When connected to a text file data source, the field data type cannot be changed in Tableau Prep 2018.2.1.


  • Tableau Prep 2018.2.1
  • Text Files


Option 1

Upgrade to Tableau Desktop 2018.2.2 or a newer version. See Tableau Desktop Downloads and Release Notes for downloads of current and previous versions of Tableau Desktop. For more information on current releases, see Upgrade Tableau Desktop and Desktop Upgrade.

Option 2

  1. Connect to text file
  2. Click + button in the top left of the window and click + Add Step
  3. Navigate to the field where you would like to change the data type (Number Decimal, Number Whole, Date & Time, Date or String)
  4. Select the blue field data type icon in the top left corner of the box, and and select desired field data type

Option 3

If an Excel file is used as a data source instead of a text file, the date can be changed to "string" before a step is added.


This behavior is related to a known issue (ID: 806084) which was fixed in Tableau Desktop 2018.2.2.
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