3 Replies Latest reply on May 10, 2018 8:35 AM by Vaibhav Bansal

    How to Row level compare linked fields in a data blend (that is from different data sources)

    Vaibhav Bansal

      Hi,

       

      I have blended 4 data sources along a datestring-field. I want to know what is the latest date available across the data sources. So, if data source A has dates till 2018-05-10 and B has till 2018-05-03, then I want the later, that is, 2018-05-03 to put in as filters do that I have my table visualization till this date.

       

      I tried doing

      1) Create a dim calculated field. If there is null for any of the datestring columns across the datasources, I will say TRUE, else FALSE which I can use in filters.

      IF NOT(ISNULL(ISNULL( [A].[Time_Field]) OR ISNULL(B.[Time_Field]))
        THEN TRUE
        ELSE FALSE
      END

      ERROR:

      All fields must be aggregate or constant when using table calculation functions or fields from multiple data sources.

      Seems like Tableau is not allowing row level comparisons among fields of different data sources (However, the fields I am using are the connection fields joining the data sources, so this should have worked)

       

      2) I tried using a similar approach but used ATTR versions of the above fields. So, I ended up successfully creating a measure field which seemed to work fine. But I need to do add filter on the top 2 (latest 2 dates), and since this is a measure field instead of a dimension, I am not able to do so. (I can only select what values I want to include or exclude, nothing like top-N which is present for dimensions)

       

      Can anyone help please?