Blending Data on Non-Matching Date Fields

Published: 27 Dec 2013
Last Modified Date: 16 Jan 2019


How to create a data blend based on date when dates do not match between data sources.


Tableau Desktop


  1. In Tableau Desktop, navigate to Data > Edit Relationships.
  2. In the Relationships dialog box, under Secondary data source select Custom, and then click Add.
  3. In the Add/Edit Field Mapping dialog box, select the date fields from the primary and secondary data sources, and then click OK twice. Aggregate the date fields at the MY (month/year) level.
  4. Edit the source data to ensure that the primary data source has all the data required. In the case of monthly data, each section should have a record for each possible Month and Year combination.  Data may be NULL or 0 as needed.

Additional Information

Removing all date values below the month level allows the date field to be more uniform across data sources.
If deeper granularity than month level data is required, consider using another field for your blend, or, in Tableau Desktop 10.0 and above, joining instead of blending. See Blend your data and Combine tables from different databases for more information.

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