Chapter 3. Relationships

Chapter 2 explored the design of the database structure, the process of analyzing the entities in the problem space and developing a set of relations that capture all the relevant data efficiently and effectively. But the relations are only one part of the data model. The associations between relations and the constraints on those associations are just as important. In this chapter, we'll look at modeling relationships, the representation of associations in the relational model. As with defining relations, the basic principles are straightforward once you understand the semantics of the data model. Certain special cases don't fit neatly into the model of relationships, however, and we'll look at some of these later.