I'm working on this personal projects, to help me learn more and be able to apply more of my Java knowledge, I wanted to work on creating my own database structure, like an Access or an Oracle... but before I get started, maybe some of you could save me some headaches...

Does anybody know which language db's like Oracle, Access, Sybase are coded in?

Is there any reason this can't be done totally in Java, or any drawbacks to using Java other than C++?

I don't think there are any problems using Java but I don't want to get far into this thing and then find out that I can't do this or that and am forced to throw things at my computer or anything else in my sight.