A rest api... how and why should it be responsible for your data? It solved a different problem.
You might not even need a database I guess, and then anything goes.
I need and like my database, and have suffered trying to get along with different ORMs. SQL is so good at what it is designed to do if you just let it.
(And why just one rest api? How about 100 restapis, some microservices, some web apps, some background workers, many different languages. One database. No ORM)