If you want to know more in detail, I'd recommend getting the sqlite sources and having a look at how it does it. It's complete, albeit not at the scale of the larger open source and commercial databases. If you want to know more in detail I recommend The Definitive Guide to SQLite which is not only a great explanation of sqlite, but also one of the most readable technical books I know. On the MySQL side, you could learn from MySQL Performance Blog as well as on the book front the O'Reilly High Performance MySQL (V2) of which the blog is one of the authors.
