How to handle “Cannot blend the secondary data source because one or more fields use an unsupported aggregation” error in Tableau
- Tableau FAQs
- December 13, 2018
The limitation on mixing data often occurs with non-additive aggregates such as MEDIAN or COUNTD.
Non-additive aggregates are functions that cannot be aggregated by dimension; instead, all calculations must be done individually. All numeric functions except MAX and MIN are non-additive aggregates.
There are several cases in which this situation can occur. Next, we’ll look at a few of them and talk about the solution:
1. The published data source is the main data source
In this case, you can try using the MEDIAN and COUNTD by blending in a published primary data source.
2. There are non-additive aggregates from a multi-connection data source with an active connection
Temporary tables are not supported by multi-connection data sources that use active connections.
Try to extract from your data source; this usually solves the problem.
3. LOD expressions are taken from a secondary source
LOD expressions are used when running complex queries with multiple dimensions at the data source level. According to Tableau, this error can also appear when using a LOD expression in a blended view.
Remove all dimensions from the secondary data source and ensure that the primary data source’s linking field is in view. Then try using the LOD expression from a secondary data source.
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