Which statement best describes a property of Third Normal Form (3NF)?

• A. All attributes must depend on the primary key transitively.
• B. A change to data in one field does not necessitate a change in another field.
• C. Data can be duplicated across rows without normalization.
• D. Tables must be denormalized to improve performance.

Answer: (B)

3NF focuses on eliminating transitive dependencies so that non-key attributes depend directly on the primary key, not on other non-key attributes. In practice, this means data is split into related tables so changes stay isolated and don’t cascade through unrelated fields. That’s why the statement that a change to data in one field does not necessitate a change in another field best describes 3NF: with proper normalization, updating a value in one place (like a department name) doesn’t force updates elsewhere (like employee data), because the dependent information resides in separate, linked tables. For example, keep department details in a separate table and link employees to departments by an ID; changing a department name updates only the department table, not the employee records. The other options describe conditions that 3NF avoids—transitive dependencies where one field depends on another, or allowing duplication, or denormalizing for performance.