On PHPBuilder.con today there's a new post from Jason Gilmore looking at using procedures and views in MySQL to refactor and simplify your site.

One particularly prominent mistake many programmers make is heavily intermingling the application logic and the domain model. PHP developers, for example, have a tendency to jam a tremendous amount of SQL into their website logic, resulting in undecipherable, unmaintainable code. [...] MySQL stored procedures and views can not only go a long way towards separating the logic and domain model, but they also can easily be integrated into PHP.

He includes several examples of how to create simple views in your database with tables from a possible e-commerce application holding order information and customer details.