The "relational data source" refers to the data source itself. In Tableau, a relational data source can be an Excel workbook, an Access database, a comma delimited text file, a MySQL database, an Oracle database, a SQL Server database, a Firebird database, a PostgreSQL database, or a Tableau Data Extract file. This is compared to a multi-dimensional data source, such as a Microsoft Analysis Services cube or an Oracle Essbase cube.
When blending data, the secondary data source is already aggregated, and thus whatever field from the primary source will need to be aggregated as well in the calculation. Would it be possible to post a screenshot of the calculation that you are trying to create?
Thanks for your response. If I understand your point, I think you've essentially answered the question when you say "when blending a data source the secondary source is already aggregated". Ideally what I'd need to do is create a relationship "pre" aggregation which is not possible with Tableau ??? It would be good if you could blend datasource in the same way that you can join tables in a SQL query
Have you found a solution for your issue? I'm working through a similar scenario and was disappointed to find that Tableau will only aggregate secondary data when blending. Let me know if you've uncovered a work around!
I have been trying a work around for the last 3 months and have had no luck. I read in another post that a Parameter will filter before the aggregation happens, but I have had no luck getting it to work. I've set parameter filters with the primary source and the secondary source and neither worked.
Good Luck to Us,