You're mixing up different things that don't nescessarily need to be addressed at the same time. SQL is the declarative programming language used to express wha

You're mixing up different things that don't nescessarily need to be addressed at the same time. SQL is the declarative programming language used to express what data you need. What type of database engine is used to execute that query is independent of the language. It could be highly scalable or it could be focussed on single user, single process. What is the problem that needs solving?