Basic Relational Database Theory

Using numerous examples, this chapter covers basic relational database theory, starting with the characteristics of tables. It discusses how to choose primary keys for tables and when to use composite primary keys. The use of foreign keys is described and presented through examples. Entity-relationship (ER) diagrams and outline notation are used throughout the chapter. The chapter also covers functional dependency, a way of analyzing the interdependence of attributes that allows one to determine table structure, and describes undesirable structures such as partial dependencies and transitive dependencies. There is further discussion of anomalies, describing insertion, update, and deletion anomalies and why they are problematic in databases. A step-by-step normalization procedure for avoiding anomalies is described through one of the database examples. Finally, the chapter explains subtypes, a technique for storing information that applies to only a small subset of the things or events described by a table.