Which normal form is defined as No duplicate information permitted; if two tables require a common field, that common field's information should be separated into a different table?

• A. 1NF
• B. 2NF
• C. 3NF
• D. Primary Key

Answer: (C)

The idea being tested is how normalization reduces data duplication by factoring out shared information into separate tables and linking through keys. When two tables share the same piece of data, putting that data in both places can lead to inconsistencies and update anomalies. Splitting that shared data into its own table and referencing it with a foreign key prevents duplication and keeps dependencies clean. This approach aligns with third normal form, which aims to ensure non-key attributes depend only on the primary key and not on other non-key attributes, thereby removing transitive dependencies and minimizing redundancy. Earlier normal forms focus on fundamentals like atomic values or eliminating partial dependencies, but they don’t address the broader separation of shared fields into their own tables. A primary key is simply an identifier for a row, not a normalization level.