11 Replies Latest reply on May 1, 2018 4:22 PM by M M

    Two secondary blended sources interfering with each other

    M M

      Hi everyone,

       

      I have several Excel sheets with some common fields where joins have been giving me duplicates, so I've tried using blending instead. This seem to be working fine except one strange side effect that I can't explain. I have the following fields:

      - In my primary source: Client ID, Team Name etc

      - In secondary source A: Team Name, Person Name etc. No Client ID here.

      - In secondary source B: Client ID, Team Name, Person Name etc.

       

      If I build a view containing data from the primary source and secondary source A only, the count of Person Names coming from source A shows correctly as 1. However, as soon as I add any field from secondary source B to the view, the count of Person Names coming from source A changes to 6, which happens to be the number of Client IDs in the primary source. It happens even if the view doesn't include the Client ID field from either primary source or source B. And obviously source A doesn't even contain Client IDs in the first place.

       

      What seems to fix the problem is either not including any source B fields in the view; or breaking the blending link between source B and primary source on the 'Client ID' field and linking them only on Team Name instead. (However, I'm cautious of this as a solution: I thought it was best to link on all matching fields, as if you omit to link a field, it could lead to double counting metrics on that field from source B)

       

      Just curious about Tableau's calculation logic causing this behaviour? How come metrics from source A are affected by the linkage between Primary and B on a field that doesn't even exist in A?

       

      Thanks everyone for your thoughts