Normalization rule-check: If a relation is already in Third Normal Form (3NF), does it not need to be in Second Normal Form (2NF)? Decide whether this statement is accurate based on the normal form hierarchy.

Introduction / Context:
This item tests understanding of the normal form hierarchy in relational design. Normalization reduces redundancy and anomalies by enforcing increasingly strict rules. Recognizing that higher normal forms include the requirements of lower normal forms helps designers reason about design quality without re-deriving every rule from scratch.

Given Data / Assumptions:

• A relation is said to be in 3NF.
• The statement claims that, in such a case, it does not need to be in 2NF.
• We consider standard textbook definitions of 1NF, 2NF, and 3NF.

Concept / Approach:
Normal forms are hierarchical. In practice, a table that is truly in 3NF must already satisfy the conditions of 1NF and 2NF. Second Normal Form eliminates partial dependency of non-key attributes on a proper subset of a candidate key. Third Normal Form goes further by eliminating certain transitive dependencies. Therefore, 3NF implies 2NF under the same candidate keys and definitions; you cannot be correctly in 3NF while violating 2NF.

Step-by-Step Solution:

Verification / Alternative check:
Attempt to construct a counterexample: a design that is 3NF but not 2NF. You will find that the 3NF criteria cannot be met if a non-key attribute still partially depends on only part of a composite key; such partial dependency violates the prerequisites for 3NF.

Why Other Options Are Wrong:

• Correct: This would contradict the hierarchy.
• “Only true for composite keys” or “depends on candidate key” are distractions; 3NF inherently assumes fulfillment of lower forms’ conditions.
• Invoking BCNF is irrelevant; BCNF is stronger than 3NF but also includes 2NF requirements implicitly.

Common Pitfalls:
Confusing “achieving 3NF” with “skipping steps.” Even if you derive 3NF directly, conceptually you also satisfied 1NF and 2NF conditions in the same design process.

Final Answer:
Incorrect