I'm a self-taught webdev too and I would strongly recommend learning SQL, not just `SELECT * ...` but really learning it!
I've been digging into postgreSQL and in quite a few applications it's possible to greatly reduce the complexity of the backend by receiving exactly the data you need from the DB. It is so much so that in cases you can even "get rid" of the backend completely (yes, no writing controllers and endpoint, etc.) by using a tool like postgREST (postgres to REST) or Hasura (postgres to graphQL)
I've been digging into postgreSQL and in quite a few applications it's possible to greatly reduce the complexity of the backend by receiving exactly the data you need from the DB. It is so much so that in cases you can even "get rid" of the backend completely (yes, no writing controllers and endpoint, etc.) by using a tool like postgREST (postgres to REST) or Hasura (postgres to graphQL)
Best of luck on your search!