Can I store Plone data in a relational database instead of the ZODB?
While the ZODB normally stores its data in a simple file on your filesystem (aka FileStorage), it is possible to have the ZODB store its data in PostgreSQL, MySQL or Oracle RDBMS backends, using RelStorage. However, because your data are still stored as Python “pickles,” this does not mean that your Plone data becomes SQL-queryable by other applications.