In this chapter you have moved beyond programming to an understanding of data, the real fuel of modern applications. You learned how to take a poorly designed table and convert it into a series of well-organized tables that can avoid a lot of data problems. You've learned about three stages of normalization. You've learned how to build an Entity-Relationship diagram. You can recognize three kinds of relationships between entities. You can build normalized tables in SQL, including pointers for primary and foreign keys. You can connect normalized tables with INNER JOIN SQL statements. You know how to simulate a many-to-many relationship by building a link table. The civilized world is safer for your efforts.