Database Design and the E-R Model

Up to this point in the text, we have assumed a given database schema andstudied how queries and updates are expressed.We now consider how to designa database schema in the first place. In this chapter, we focus on the entityrelationship data model (E-R), which provides a means of identifying entities to be represented in the database and how those entities are related. Ultimately, the database design will be expressed in terms of a relational database design and an associated set of constraints. We show in this chapter how an E-R design can be transformed into a set of relation schemas and how some of the constraints can be captured in that design. Then, in Chapter 8, we consider in detail whether a set of relation schemas is a good or bad database design and study the process of creating good designs using a broader set of constraints. These two chapters cover the fundamental concepts of database design.