What exacltly do you mean by 'extracting'?  If you want to load tables defined in Unity into a database, I would indeed do this using job clusters and a notebook.
If you want to extract some data once in a while into a csv f.e., you could perfectly do that with any sql tool using odbc or even in databricks ui itself.

Or do you want to have some kind of a SQL api where applications can run queries?