You're right, I'm not being specific enough. By "break into my db server" I really mean "obtain a copy of my database"
How would the attacker do that? Gaining shell access to my server and doing a live dump of the db (only I have access to the machine, no shared-hosting or anything), stealing my backups, etc..
Chance of the attack happening Hopefully very low but since I'm dealing with medical info I'm compelled to encrypt the database anyway
the cost of successful attack A whole lot of badness
the costs of the possible counter-measures and the effectiveness of the possible counter-measures The point of my post is to find out if any counter-measures exist, suggestions welcome!
I'm not so much concerned with SQL injection in regards to this question although I totally agree it's a really tough hole to protect against and something I'll also need to adrress in my code.