Makes for fun/interesting practice if people are willing to download mysql or oracle xe if they are bored.
I'd consider putting oracle xe on the server here and creating a sandbox for it, but I'm not sure exactly what the licensing terms allow.
They state that it's "free to develop, deploy, and distribute", but I don't know if that covers its use here. They also mention that it's intended for "Educational institutions and students who need a free database for their curriculum", but again I don't know if that includes our using it here. (??)