A relation that is free of all modification anomalies is in which normal form?
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AFirst normal form
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BSecond normal form
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CThird normal form
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DDomain/key normal form
Answer
Correct Answer: Domain/key normal form
Explanation
Introduction / Context:Higher levels of normalization progressively remove sources of redundancy and anomalies. The strongest commonly cited form in theory ensures complete freedom from modification anomalies.
Given Data / Assumptions:
- First normal form removes repeating groups and enforces atomic values.
- Second and third normal forms address partial and transitive dependencies with respect to keys.
- Boyce–Codd and beyond tighten conditions further; domain/key normal form is even stronger.
Concept / Approach:Domain/key normal form states that every constraint on the relation is a logical consequence of the domain definitions and key constraints. Under this condition, update, insert, and delete anomalies are eliminated in principle.
Step-by-Step Solution:
Recall which normal forms still permit certain rare anomalies (even BCNF can in edge cases).Recognize that domain/key normal form is the theoretical target where all constraints derive from domains and keys.Select domain/key normal form as the answer.Verification / Alternative check:Classic literature acknowledges that domain/key normal form is sufficient to guarantee freedom from all modification anomalies.
Why Other Options Are Wrong:
- First, second, and third normal forms reduce but do not eliminate all possible anomalies.
Common Pitfalls:Assuming third normal form or BCNF automatically eliminates every anomaly. Edge cases still exist; domain/key normal form is stricter.
Final Answer:Domain/key normal form