Maggie Nelson has pointed out an article in the most recently published edition of php|architect magazine (the February 2008 issue) that's an introduction to database design for programmers (by Mac Newbold).
It's a pretty good article about database design and I think all PHP developers who are just starting to integrate databases in their applications should read it. However, there are a few things I'd like to add and point out.
The "blurb" for the article mentions MySQL, PostgreSQL, Oracle, Microsoft SQL, SQLite and database schemas. You can find out more about this issue, including how to get your own copy, from the php|architect website.