NetTuts.com has posted the second part of their series looking at the "guts" of a typical WordPress installation. In the first part they gave an overview of the structure and contents of the various database tables. In this second part they get more into the relationships between them.

In the first part of this series on data in WordPress, I gave an overview of the WordPress database tables, and which tables are used to store what kind of data. In this second part, I'll outline how WordPress manages the relationships between that data. As you'll see, WordPress uses three kinds of data relationship - one-to-one, one-to-many and many-to-many. I'll look at each of these and what they mean for your WordPress site.

He goes through each of the relationship types and includes examples from the WordPress database to illustrate them. He then gets into a bit more depth, talking about the specifics of some relationships like: posts-to-users, posts-to-comments, comment-to-comment and the structure of the many-to-many relationships too.