2NF Removes Which Kind of Dependency?
In relational schema normalization, Second Normal Form (2NF) is specifically designed to eliminate partial dependency.
For the multiple-choice question: “2NF removes which kind of dependency?” the correct option is:
- (ii) Partial
At a high level:
- 2NF targets partial functional dependencies that arise when a table has a composite (multi-attribute) key and some non-key attributes depend only on a subset of that key.
- 3NF/BCNF are then used to handle other issues such as transitive functional dependencies.
- 4NF is used to handle multivalued dependencies.
Key terms for this question: 2NF, partial dependency, transitive dependency, multivalued dependency.
Database Normal Forms (1NF, 2NF, 3NF, BCNF, 4NF) - Quick Explanation
How to decide what 2NF removes (conceptual checklist)
- 1Step 1
Determine the table’s candidate key(s). If there is a composite key (multiple attributes), partial dependencies can exist.
- 2Step 2
Look for functional dependencies of non-key attributes on only a subset of a composite key (this is the hallmark of partial dependency).
- 3Step 3
Enforce that every non-prime attribute is fully functionally dependent on the entire candidate key; violations are what 2NF fixes.
- 4Step 4
Use: 2NF → partial functional dependency; 3NF/BCNF → transitive functional dependency; 4NF → multivalued dependency.
Fast exam rule
If the options include partial vs transitive vs multivalued, then 2NF corresponds to partial functional dependencies.
Common confusion
Do not confuse 2NF with 3NF: transitive dependency (A → B and B → C) is not what 2NF is meant to remove; that's the next stage (3NF/BCNF).
Which dependency type corresponds to which normal form?
Directionally: what each normal form is designed to eliminate.
Answer details for the given options
2NF dependency quick self-test
Knowledge Check
2NF removes which kind of dependency?