1 Reply Latest reply on Nov 9, 2019 4:38 AM by Michael Gillespie

    Tableau Utility - Minus Queries between Source and Target

    Akshay Pallerla

      Hi Community folks,


      I have the following requirement, rather thought process. I need your help in figuring out if it is possible to implement a solution.


      Our client planned to move their "On-premise" datawarehouse to a cloud-hosted one. Now, the task in hand is to validate if the migration for almost 200 tables was done properly or not.

      I was thinking is there a way if we can connect Tableau to two different database connections, source data from each of them and do a kind of minus query dynamically.


      The user shall select the database he is interested in and we should take advantage of data dictionaries in the corresponding database provider and list the available tables automatically. And When the user selects a particular table, it should figure out the columns it has and performs a minus between source (On-prem connection) and target(Cloud) connection and list the results on the dashboard.


      If the source and target match, migration is successful. If not, the rows returned shall need to be analyzed and figured out.


      Shawn Wallwork Sandeep Das Dmitry Chirkov

        • 1. Re: Tableau Utility - Minus Queries between Source and Target
          Michael Gillespie

          You can't do math between two data sources if there is no connection between those data sources.  You'll have to create a join or blend if you want to do this.


          You could do a dashboard where you compare certain metrics side by side in separate vizzes, one for each data source.


          You also can't list the tables in a given database in a Tableau viz unless there is some metadata layer you can attach to with a list of those tables.  You can see them in the data source tab but you can't reference the table name in a Tableau calculated field.  If you have a tool like Alteryx you could write a transform that would expose that metadata to Tableau, but it's not something you can do out of the box.  I don't think you can do that with Prep, although I'd be delighted to be wrong about that.