There are a variety of ways to accomplish this. Since your different views are essentially different flows, I would build them each as different REST API mappings if you're able to change your URI to use the path rather than query parameters for the views.
If you must send the action as a query parameter then you could take a look at the expression filter in the tMap/tXmlMap component. This would allow you to conditionally join/query to your different databases and produce different outputs to different tRestResponse components. The expression filter is available by clicking the button that has a white arrow with a green "+" sign on it.