You can access RDBMS data using the SQL Statement action. Please see the SQL Statement action within the Rules Design Reference for more details. Using the WebMaker Data Source capabilities will set-up Rules to process the SQL data for simple actions. For more complex SQL scenarios, it will be necessary to access the Rules to refine the SQL statements.
Within each SQL operation you can either define new database connections or reuse existing database connections that have already been defined. You can also access the database connection information from the WebMaker Studio Deployment screens, accessible from the Project tab.