Java How to Program, Early Objects, 11th Edition

24.2 Relational Databases

A relational database is a logical representation of data that allows the data to be accessed without consideration of its physical structure. A relational database stores data in tables. Figure 24.1 illustrates a sample table that might be used in a personnel system. The table name is Employee, and its primary purpose is to store the attributes of employees. Tables are composed of rows, each describing a single entity—in Fig. 24.1, an employee. Rows are composed of columns in which values are stored. This table consists of six rows. The Number column of each row is the table’s primary key—a column (or group of columns) with a value that is unique for each row. This guarantees that each row can be identified by its ...