Sams Teach Yourself SQL in 21 Days, Fourth Edition

Understanding the Normal Forms

In the next section, and following subsections, we will be discussing the normal forms. The normal forms are ways of measuring the levels, or depth, to which a database has been normalized.

The three most common normal forms in the normalization process are

• The first normal form
• The second normal form
• The third normal form

Of the three normal forms, each subsequent normal form depends upon normalization steps taken in the previous normal form. For instance, in order to normalize a database using the second normal form, the database must already be in the first normal form. In order for the database to be normalized using the third normal form, the database must already be in the second normal form (which means that, ...