How to Execute a Inner Join using REST API

Hello
I am using the REST Sql Datasource API.
It works fine. I can execute queries and get desired output.
But I am now trying to execute a Inner join query. There is no filter condition.
Its A simple query that matches all records between 2 tables and gets all the fields.
Somehow the Inner join query is not working. I am getting internal server error.

I am not sure what is the problem here. Is the query not defined properly. (Query runs fine on DB).
Does the REST SQL DATASOURCE not allow join queries ??
What can i do to execute joins and fetch data ??

Please suggest.