6 Replies Latest reply on Apr 7, 2016 1:50 AM by Andrew Watson

    Data Blending is showing incorrect result.

    Somok Sarkar

      Hello Everyone,


      While working on a report I found the results are coming as inaccurate as I was using Data Blending.


      My requirement is I want to analyze the Occupancy rate, Average Daily Rate etc of a Hotel based on Events. The Events records and the booking records are coming from two separate data set. I am blending them on state name and the zip codes. Now if I analyze the result of the event "Atlanta Halks - Boston Celtics" the overall occupancy is showing 76.59% which should be 88.73%.


      I have shared the files can someone kindly point me the mistake that I am making while creating this report?




        • 1. Re: Data Blending is showing incorrect result.

          Hi Somok,

          Normally data blending will work correctly when you have the same number of columns in two data sources and the values inside these columns are case sensitive. For ex: in data source 1 if the state is like Arizona and in data source 2 it is like arizona in that case the results wont appear or its not correct.

          Like that we need to check whether the values are correct in the both the columns between two data sources.

          You can do this practice by dragging and dropping the blended columns in one sheet and check whether both the values between the sources are same or not.

          Hope its useful.

          I can't open your workbook because I am using Tableau 9.1

          • 2. Re: Data Blending is showing incorrect result.
            Swarup K

            Cross check the data in the excel sheets and check whether data is matching or not, as 'kumar' said check for case sensitive.

            I am using earlier version not able to open the workbook.

            • 3. Re: Data Blending is showing incorrect result.
              Andrew Watson

              Please check your numbers and see if it is actually reporting incorrectly. This is from 'Main Sheet', where you get your Occupancy:



              And this is when the data behind the blend is expanded - showing the blend fields:



              Your joining fields are questionable as I assume there should be some time based blending required as well if trying to join to an event - the way you're joining is showing Occupancy overall for the Zipcode/State combination.


              For your interest adding a join from Start Date to Date gives the following:


              • 4. Re: Data Blending is showing incorrect result.
                Somok Sarkar

                Hi Andrew,


                Many thanks for lighting this up. As you have showed I have blended the data now on the dates. However now as you see from some of the events the occupancy is coming as null. When I check the excel sheets that shouldn't be null at all.


                Eg : Event Name  - "Atlanta Hawks - Chicago Bulls"


                The tableau report shows null however the excel file shows there are data.


                Can you please advise me how to rectify this? I have attached the excel files.

                • 5. Re: Data Blending is showing incorrect result.
                  Somok Sarkar

                  Hi Kumar,


                  Thank you for your reply.


                  Actually The Column numbers are different here. I am trying to blend the data set on Date, State and the post codes.


                  Event data set includes the event date and the event name and the location ; The hotel booking data has booking date, hotel name & location, Occupancy.


                  I am trying to derive as on 01-Jan-2015 Id there is an event on post code 70707 then what was the occupancy of the hotel at the postcode 70707 for the same date. Any idea how to overcome this issue?


                  As Andrew suggested I am getting the data for some events but some are blanks now.

                  • 6. Re: Data Blending is showing incorrect result.
                    Andrew Watson

                    Yes, blending on dates can sometimes gives unexpected results - check out this post: How to join - data blending - date fields in Tableau


                    Change the joins to as follows and it should work better:



                    To help sense check the numbers I recommend putting the Start Date field into the data you can manually check whether right or wrong numbers are being returned and whether your joins need to be further tweaked: