View http://scotty-t.com/2012/01/30/understanding-mysql-in-wordpress/
If you’re looking to improve your low level WordPress querying chops, this article is great. When building more application-like pieces of functionality in WordPress, it’s really important to understand what’s happening under the hood (at least to a degree) so you can ensure that you’ve taken care of potential bottlenecks when your project gets utterly slammed with traffic.
