4 Replies Latest reply on Oct 23, 2018 10:04 AM by Akram Ebrahim

    How Blending works in Tableau

    siva Nageswara Rao

      Hi,

       

      This is my view about blending in Tableau. Please correct me if my opinion on blending is wrong.

       

      I'm assuming that blending behaves like a left join/left outer join. Two different quarries will be sending to data source and data will be fetched in to the Tableau and the joining will be happen in Tableau. Till now no confusion.

       

      If I apply a filter to the secondary data source only by using the option in the filters All Using this Data source only. So the filter will be applied only to the secondary data source and that to data source level means filter will be applied at source level and filtered data will be fetched onto the Tableau.

      Important note that Two data sources are being joined by a common filed.

       

      Now If I applied a filter on secondary data source because that is developed by using this option All Using this Data source only,  so data will be filter at source level and rest of the data will be joined (assuming left join) with the primary data source.

       

      As we applied filter only to the secondary data source data will not be filtered in the primary data source but here data is filtering. Is that because of join field. As It was a left join data should not be filtered in primary data source it should return all the rows from primary data source and what are the matching rows from secondary data source.

       

      Is assumption is correct?If it is not correct then, Is there any way to filter data at source level and joining after the filter?

       

      Thanks,

      Siva