Difficulty: Easy
Correct Answer: A functional dependency between two or more nonkey attributes.
Explanation:
Introduction / Context:
Transitive dependencies create hidden redundancy by allowing a non-key attribute to determine another non-key attribute indirectly through the primary key. Recognizing and removing them is key to achieving Third Normal Form (3NF) or Boyce–Codd Normal Form (BCNF).
Given Data / Assumptions:
Concept / Approach:
A transitive dependency occurs when key → A and A → B, where A and B are non-key attributes. Thus, key → B holds transitively via A. This creates redundancy and potential anomalies, because changing A may require updating B everywhere A appears.
Step-by-Step Solution:
Verification / Alternative check:
Group by A and check whether B varies within those groups; if not, A determines B. Combined with key → A, that implies a transitive path key → B.
Why Other Options Are Wrong:
Dependencies among key attributes are not the target; keys are determinants by definition.
“In 1NF/2NF” describes normal forms, not the dependency type itself.
Common Pitfalls:
Confusing derived/calculated values with dependencies; mixing up partial and transitive dependencies in composite-key situations.
Final Answer:
A functional dependency between two or more nonkey attributes.
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