Error "Cannot blend the secondary data source because one or more fields use an unsupported aggregation" when Data Blending

Published: 13 Mar 2017
Last Modified Date: 29 Mar 2018


When working with data blending using non-additive aggregates such as COUNTD, MEDIAN, CEILING, FLOOR, and RAWSQLAGG, you may see the following error message if you hover your mouse cursor over one of these fields: 
"Cannot blend the secondary data source because one or more fields use an unsupported aggregation"

Note: This error message can also appear when you use a level of detail expression in a view that uses data blending. The linking field in the primary data source must be in the blended view before you can use an LOD expression from the secondary data source, and no other dimensions from the secondary data source can be included in the view.


  • Tableau Desktop
  • Data Blending


Use one of the following workarounds

  • Use table joins to combine the data rather than data blending. If the data comes from different data sources, then you may be able to use cross database joins to join the tables.
  • If you need a non-additive aggregate on the primary data source, but your data source does not support temporary tables, consider creating an extract. Tableau data extracts support temporary tables.

  • If you are using a secondary dimension, try changing the dimension to an attribute instead. To do that, right-click the field in the view, and select Attribute.
    Important: Selecting Attribute might replace values with an asterisk (*). This indicates that there are multiple values in your data at this level of detail and Tableau can't determine which to display.

  • Using the Number of Records field might be an alternative to using COUNTD, depending on your data.
Note: These suggestions may not work if you explicitly added linking fields by clicking the link icon in the secondary dimensions window. 

Alternative workaround

If a non-additive aggregation from the primary data source is in the view, you cannot use a group created in the primary data source in the view.

  • To work around this limitation, convert the group to a calculated field.

Non-additive aggregates are only supported for the primary data source, if that data source is a relational data source that allows the use of temporary tables. Non-additive aggregates are not supported for any secondary data sources.


Data blending has some limitations regarding non-additive aggregates such as COUNTD, MEDIAN, and RAWSQLAGG. These limitations cause certain fields in the view to become invalid in certain circumstances.
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