Backend as a Service (BaaS) with RDBMS / SQL and Unity integration

Hello, i'm in desperate need of a backend service for unity, that has a unity SDK - just like gamespark - , but has the possibilty to use a relational database / SQL (not NoSQL). Is there such a thing?

Or maybe re-phrased: What service would you use when you are building a game in unity that needs to fetch and store data (not as simple as highscores, more like: text<->textregion<->tag<->links_between_tags relations) from somewhere online? (besides user auth, etc.)