In this chapter, I explained the fundamentals of good database design, and we learned how MySQL and, for that matter, all relational database management systems, provide support for the representation of different types of relationships between entities. From your meagre understanding of one-to-one relationships, you should now have expanded your knowledge to include many-to-one, one-to-many, and many-to-many relationships. And in the process, you learned a few new features of common SQL commands. In particular, you learned how to use a SELECT to join data spread between multiple tables into a single set of results. In "A Content Management System", you'll use all the knowledge you have gained so far, plus a few new tricks, to build a basic content management system in PHP. The aim of such a system is to provide a customized, secure, Web-based interface that manages the contents of the database, instead of requiring you to type everything in by hand on the MySQL command line.