What kind of database are you using? Was the Tableau data source built using JOINs? If so, you should see the JOIN structure from "Data Source" pane (in your tdsx file). There you should find all the tables that were used to create the data source.
Thank you Shiva for the prompt reply:
1. We are using Microsoft SQL Server:
2. We are not sure about Joins3. I don't see any joins on the Data Source Pane.
I completely forgot that we use Alteryx to build those data sets.