DB table data export formats

Hello folks,

I wasn't sure where to post this question so I'm starting here.

I've been tasked with conceiving an architecture for a system that will need to automatically (programmatically without human intervention) pull data from various kinds of databases (only one table at a time for now). Ideally, the export format would be CSV or "flat file."

My questions are:

First, what is the most common export format supported by various DB products: CSV, JSON, flat file, other?

Second, most likely I'll be expected to target a Java environment for this system that will programatically initiate a pull from the DB. I know there are JDBC drivers to connect to many DB products. Are there DBs that don't have JDBC drivers and, if not, what are some other interfaces available?

I know these are very general questions not specific to any DB product. I'm just trying to wrap my thoughts around the technical landscape I might face at the DB side.

Many thanks...