In short, yes. This is possible.
If you are using Tableau 10, this is actually very easy, since one of the new features allows you to Filter Across Data Sources. Even in Tableau 8 or 9, this could still be achieved using Action Filters and/or Data Blending. It's tough to provide you with an exact solution without a packaged workbook to work with, though.
I have attached to excel files and a Tableau Workbook to the original post that could be used as a starting point.
Let me know if this helps. Thank you.
Hey Ashwin. It looks like you're already 99% of the way there. One minor change is all you need to achieve this.
Go to your dashboard and in the menu bar at the top, select the Dashboard dropdown, then click Actions. You should already have an action filter in the window, so double click that to edit it. If not, just select Add Action > Filter. The only change you need to make is in the Target Filters section at the bottom. Click Selected Fields, then Add Filter, then set it so Tableau matches Department ID in poc1 with Department ID in poc2. If you want, you could also deselect the Run on single select only option as well, so that you can filter on multiple departments at the same time.
Once all that is done, just click OK and your dashboard should work as you intended.
Drill Down POC.twbx 27.0 KB