Best resources for an engineer to learn databases?

I’ve picked up a few programming languages by now, and I feel pretty comfortable understanding the differences (garbage collection, interpreter vs compiler, type systems, etc.)

Im at a point now where I feel like I “know” programming languages and could pick up a new one or choose the appropriate one for a project without a ton of effort

But for databases- I know a little bit, but i wouldn’t really know how to start choosing a database, or moving business logic like replication or rpc calls into a database.

Does anybody know a good resource? I see lots of courses online targeted at DBAs, Im not sure if that’s where I should start, or if I should do hello worlds or some equivalent of leetcode like I do for picking up a new language