If you're relatively new to PHP development or have just meaning to get into using relational databases with your application, you should check out this new post from NetTuts giving a "for dummies" approach to learning about RDBMSes.
Web apps can be split into two major components: a front-end that displays and collects information, and a back-end for storing the information. In this article, I’ll demonstrate what a relational database is, and how to properly design your database to store your app’s information.
They describe the usage of a database in several steps (no code is included, just SQL at the end):
- Get Some Data
- Remove Repetitive Data Across Columns
- Remove Repetitive Data Across Rows
- Linking Tables with Keys
This is followed by links to a few of the different RDBMSes out there and a brief introduction to what SQL is and what it looks like.