I've read in a couple of places that Derby/Java DB is included in Java SE 6, e.g. http://java.sun.com/developer/technicalArticles/J2SE/Desktop/javase6/beta2.html but I can't find anyone who has used it without installing it, including it on the classpath, etc.
What's going on? If it's included, why does everyone install another copy?
You need the JDK, not the JRE.