III.1.4. Third Normal Form
A table in third normal form must be in the second normal form and every non-primary key column must be non-transitively (or directly) dependent on only the primary key. In other words, if any non-primary key columns are directly dependent on other non-primary key columns, then the table isn't in the third normal form.
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Consider Figure 1-5, which isn't in the third normal form because of the CustomerPhone column. The CustomerPhone column is directly dependent on the CustomerName column for meaning. Because this customer placed this order, then the phone number is indirectly associated with the primary key of OrderID, showing a transitive relationship between the CustomerPhone and the OrderID.
Figure III.1-5. An Orders table that isn't compliant with the third ...
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