Data Is Duplicated After Incremental Refresh

Published: 26 Feb 2015
Last Modified Date: 28 Jul 2020


When using incremental extract refreshes, data duplication might occur.


  • Tableau Desktop
  • Extract configured with a DATETIME increment key


Option 1

Wrap the DATETIME field in a truncate function at the datasource. For example: 

To view an example of the Trunc(date) function for Oracle Database: Database SQL Reference: Trunc* in the Oracle Knowledge Base. 

Option 2

Convert the relevant table joins to CustomSQL to CAST the DATETIME key as a truncated DATETIME field.
To view an example of the CAST function see Database SQL Reference: Cast* in the Oracle Knowledge Base. 

Option 3

Create a view at the data source. For more information, see Create a SQL View* (external site,

*Although we make every effort to ensure links to external websites are accurate, up to date, and relevant, Tableau cannot take responsibility for the accuracy or freshness of pages maintained by external providers. Contact the external site for answers to questions regarding its content.


The date time field in the database is more precise than the date time that is recognized by Tableau Desktop.


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