Hi Chetan,
If you look into the execution plan (Visual plan) for the query against the HANA table / Information model object, you can see that any joins are performed on the columns. Please refer to the following links to understand more about the column store and column operations in HANA. It will help you understand how the joins are performed.
http://scn.sap.com/people/neha.singla/blog/2012/02/20/column-store-in-sap-hana
http://scn.sap.com/thread/2124636
You do not need to perform any distinct operation explicitly. Hope this helps.
Regards,
Ravi