I'm working on a website that could eventually have a very large database. The website will be an art community not until deviantART. I'll be running a lot of queries for analyzing how the site is used. I expect some of the queries to kill the database because I don't know how to optimize SQL queries (yet). I'm starting out with a small linux VPS and would move to physical servers in the future.
Which database would scale the best given this situation?