Databases play an important role in enterprise applications, so you should definitely read up on relational databases and SQL. Whether learning OO Base will help with this, I'm not sure (is it SQL-accessible?) Once you master SQL, learning JDBC isn't hard, and what with EJB, Hibernate etc. it's becoming less important, since it's becoming more likely that you won't see pure JDBC, but rather some layer on top of it.
I brought this back from the farm where they grow the tiny ads:
Free, earth friendly heat - from the CodeRanch trailboss