This is a very conceptual question and looking for advice or examples you may know about. I'm just getting back into development after a very long hiatus in a sales career, so please excuse me if my thoughts or questions seem simplistic or outdated.
The data for a very large number of implementations is moving off-site from an SQL server to be accessed by a very few specific RESTful APIs. Rather than spending the man hours redeveloping each iteration of the data access to REST GET requests, I wonder if there's a better way. My idea is to develop (or find) an SQL layer that (invisible to the client) adapts the SQL queries into REST requests and returns the data in SQL format. All then, the client would need to do is switch it's SQL source to the new "SQL service" and automatically retrieve the data from the REST API formatted to suit the application.
This may not be possible to create a universal REST API translator because the data schemas are so different between JSON/XML and SQL generally speaking, but I wonder if because the APIs I am accessing use the same data schema if something couldn't be developed for my specific implementation. Perhaps I would need to tweak this adapter layer application for each client's nuances in their SQL queries, but maybe this would save development time for each client not wanting to rush to total redevelopment of their platform.
I wonder if anything like this has been accomplished before, is even possible, and what issues lie ahead. Is this too much of a band-aid that will break down with data changes? Could this be lightweight enough to work without significant slowdowns? Any advice or thoughts are greatly appreciated.