The part about SQL makes little sense to me. The author seems to be equating relational databases with SQL, but I don't know why. Yes, that's how everyone learn

The part about SQL makes little sense to me. The author seems to be equating relational databases with SQL, but I don't know why. Yes, that's how everyone learns about relational databases (or the approximation thereof that SQL provides), but SQL is just one (not so awesome) language for interacting with a relational database. You could provide a binary protocol instead of or in addition to SQL for any relational database. The protocol is not the implementation!