Accounting Information Systems: The Processes and Controls, 2nd Edition

THE NEED FOR NORMALIZED DATA (STUDY OBJECTIVE 5)

Relational databases consist of several small tables, rather than one large table as in the flat file database. The small tables in a relational database can be joined together in ways that represent relationships among the data.

For example, examine the tables and relationships of a Microsoft Access^® database in Exhibit 13-6. Each box is a table, and the field names are listed in each box. The bolded field is the primary key. The primary key, the unique identifier for each record in each table, is used to sort, index, and access records from that table. The lines between boxes indicate the relationships between the tables. The relationships indicated in these tables are one to many. For example, one customer (CustomerID), can have many orders listed in the Orders table. Note that the Customers table and the Orders table are linked by CustomerID. In the Orders table, the CustomerID field is a foreign key field. In other words, CustomerID is in a different (foreign) table, but is needed in the Orders table to establish the link between Customers and Orders.

Exhibit 13-6 A Relational Database in Microsoft Access®

These separate tables and the relationships between the tables are what establish the advantage of a relational database. The advantage is that a relational database has flexibility in retrieving data from queries. The developer ...