However, a serious pitfall known as a redundancy anomaly endangers all three of these goals. Redundancy anomalies occur when database files and the relationships that combine them are poorly designed. This poor design can lead to useless repetition, wasted disk space, added work, and more errors. To address these problems, a powerful technique called normalization has been developed.
Normalization is a process of strict adherence to certain guidelines known as normal forms .
A normal form is a design rule that ensures the most efficient and effective use of the data managed by the system. We will introduce the four most basic normal forms, and show how to avoid violating them when designing a table or a query. Before doing this, it would be helpful to examine the most fundamental and, unfortunately, the most common flaw in table design. When this lone table is included in the query shown in Figure 1, its output table resembles the one in Figure 2. Field Field Name Type Width Index 1.