SQL Database written in pure and 100% Java. It can be used as embedded, server, or in-memory database. Batteries included; I mean, it comes with a web-based admin console to manage your databases. And the performance? Men!! Speed of light. OK, that's exaggeration. The thing is, performance comparison is hard to get right due to many factors. But if you're in the to-see-is-to-believe camp, I suggest that you test it yourself and see how it's jaw-dropping performance outshines its competitors. I will not say anything more about H2. I want you to try it yourself and feel the euphoric experience that leaves you loving your job as a software developer. But I have a bit of warning, though: When you touched H2 Database, you would never look back again to JavaDB/Derby.
Comparison to Other Database Engines