7 Replies Latest reply on Jul 8, 2016 12:31 AM by Dmitry Chirkov

    Bug with connections and linking?

    Bobo Wieland

      I constanly get the following error message when draging a dimension to the work sheet:

      "The primary and secondary connections are from tables in the same data source. Instead of linking the connections, use the Data menu to join the data. Joins can integrate data from many tabled and may improve performance and filtering."

       

      I don't think this is correct. The connections I have are to two different MySQL instances and the data source are identical Custom SQL (except for a hard coded text field indicating from which db instance the data comes from). The one difference between the connections is the port used.

       

      Is this a bug?

       


      I have a follow-up question too, but I don't know if this is because of the issue above or something I do wrong (if it's a separate issue I can post it in a different thred perhaps): The hard coded text field above is a two character country code. Preferably I would like to treat the data from the different data connections as one data source. This doesn't really seem to work? I can't get data grouped by country code (and date) as I would like (but since I'm only weeks into testing Tableau (trial and error approach) I'm hopeful that It's me, not Tableau)

        • 1. Re: Bug with connections and linking?
          Bobo Wieland

          Update: Found an answer to my follow-up question here using Data extracts and adding data from another data source.

          • 2. Re: Bug with connections and linking?
            Dmitry Chirkov

            I assume you are connecting to the same MySQL server but different databases, correct?

             

            If yes, then it kinda could be a bug since in UI we don't allow joining tables from different databases yet that's totally possible via Custom SQL...

            • 3. Re: Bug with connections and linking?
              Dmitry Chirkov

              Bobo, let me ask you this - are you using blending on purpose (i.e. your data is aggregated at the different levels) our you'd rather just join two databases directly but just can't?

              • 4. Re: Bug with connections and linking?
                Bobo Wieland

                Thanks for your replys Dmitry!

                 

                I am not connection to the same server. It's identical MySQL instances regarding databases and tables, but holds data for different geographical regions. The sit on the same physical server and the only thing that differs is the port I'm connecting to and the data in the tables.

                 

                Connection 1:
                host: db.server1
                port: 3301
                user: myuser
                pass: mypass

                db and table: logdb.sales_summary
                data in table:
                ...
                date: 2016-07-07
                nbr_of_sales: 67
                ...

                Connection 2:
                host: db.server1
                port: 3708
                user: myuser
                pass: mypass

                db and table:
                logdb.sales_summary
                data in table:
                ...
                date: 2016-07-07
                nbr_of_sales: 175
                ...

                 

                What I would like to do in Tableu is to treat these two tables as one. My inital approach was to access them through a custom SQL adding a region specific column. With that I could work with it using one of the connections as master and creating an extract and then adding the other(s) data. It worked, but not great since I had to have all the connections visible in my work sheet even though I only used one (and this is not just two connections. Just testing with two. If I should use all there would be perhaps 20-30 connections)

                 

                However. Figured out that we probably can't work this way and have to aggregate our allready aggregated data to one single instance to be able to utilize Tableau. But I'm still thinking that the error message I got is kind of a bug since it's definitly NOT the same data source.

                1 of 1 people found this helpful
                • 5. Re: Bug with connections and linking?
                  Dmitry Chirkov
                  1. I found a place in the code where we are totally not checking the port - I'll file a bug for that so thanks for a good find.
                  2. Have you heard about "cross-database joins" feature that is about to ship in 10.0? This writeup is pretty good. From the sound of it, however, you need a Union though, no?
                  1 of 1 people found this helpful
                  • 6. Re: Bug with connections and linking?
                    Bobo Wieland

                    From the article you mentioned:

                     

                    "With cross database join functionality, you can spend time with the end-userprototyping with actual data, rapidly adding and changing data as new insights occur, and changing requirements as needed. Once the solution is delivered, the results can be used as the requirements for the data warehouse project, thus eliminating unsuccessful projects and inefficient re-work."

                     

                    This sounds exactly as what I'm doing all the time.

                     

                    And yes, I probably would need a cross-database union. I can't immediately from the article see that this shouldn't work though?

                    • 7. Re: Bug with connections and linking?
                      Dmitry Chirkov

                      Not yet, my friend... not yet ¯\_(ツ)_/¯