Executing an Inner Join over RFC on Database Tables in SAP System

You can do this by creating your own function module that can perform selection as per the requirement.

You could also use to create a database view and that can be used to call RFC_READ_TABLE. Also, check for prebuilt SAP connectors provided by companies for SQL joins:

http://www.plsapconnector.com/