DA0-002 Data Concepts and Environments Practice Question
A table Orders has OrderID (primary key), CustomerID, and CustomerEmail. During analysis, it is found that CustomerID uniquely identifies CustomerEmail. Which normal form is violated if both CustomerID and CustomerEmail are stored in this table?
⚠ Common exam trap
Candidates often confuse transitive dependencies with partial dependencies, mistakenly thinking that because CustomerID is not part of the primary key, the violation is 2NF rather than 3NF.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Third normal form (3NF)
The table violates Third Normal Form (3NF) because CustomerEmail is transitively dependent on CustomerID, which is not a candidate key. In 3NF, every non-key attribute must depend only on the primary key (OrderID), not on another non-key attribute. Since CustomerID uniquely identifies CustomerEmail, CustomerEmail depends on CustomerID, not directly on OrderID, creating a transitive dependency.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Second normal form (2NF)
Why it's wrong here
2NF requires full functional dependency on the whole primary key. Since CustomerEmail does not depend on OrderID, it is not fully dependent, so it violates 2NF? Actually, 2NF violation occurs when a non-key attribute depends on part of a composite primary key. Here primary key is simple (OrderID), so 2NF is not violated. The correct violation is 3NF.
- ✓
Third normal form (3NF)
Why this is correct
CustomerEmail depends on CustomerID, which is a non-key attribute, creating a transitive dependency violating 3NF.
- ✗
No violation
Why it's wrong here
There is a clear transitive dependency.
- ✗
First normal form (1NF)
Why it's wrong here
1NF is satisfied; attributes are atomic.
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