Apache/Derby 10.5 is about to be released, and Knut Anders Hatlen has written a great blog entry about one of the new features: Generated Columns. (Knut himself has also worked on some important core-level feature that improves locking mechanisms within Derby.)

Derby is an all-Java database to which Sun engineers in the Java DB team contribute.

Java DB is Sun's release of Apache/Derby! In Java DB, even the database user-defined functions can be written in Java!