25.2. 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 25.1 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 an employee. Tables are composed of rows, and rows are composed of columns in which values are stored. This table consists of six rows. The Number column of each row in this table is the table’s primary key—a column (or group of columns) in a table with a unique value that cannot be duplicated in other rows. This guarantees that each row can be identified by its primary ...
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