DA0-002 Data Concepts and Environments Practice Question
A database table has columns: OrderID (primary key), ProductID, CustomerID, CustomerName, OrderDate, ProductName. All products are purchased only by the customer who placed the order. Which normal form violation exists if CustomerName depends on CustomerID?
⚠ Common exam trap
Candidates often confuse transitive dependencies (3NF violation) with partial dependencies (2NF violation) or think that any dependency on a non-key attribute automatically violates BCNF, but the specific scenario of CustomerName depending on CustomerID is a textbook transitive dependency that breaks 3NF first.
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 CustomerName depends on CustomerID, which is not a candidate key (the primary key is OrderID). 3NF requires that every non-key attribute be non-transitively dependent on the primary key; here, CustomerName is transitively dependent on OrderID via CustomerID. Since CustomerID is a non-key attribute (it is not part of the primary key), this transitive dependency breaks 3NF.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Boyce-Codd normal form (BCNF)
Why it's wrong here
BCNF requires that every determinant is a candidate key; here CustomerID is a determinant but not a candidate key, so BCNF is also violated, but the most immediate violation is 3NF.
- ✓
Third normal form (3NF)
Why this is correct
CustomerName depends on CustomerID, which is not a candidate key, creating a transitive dependency and violating 3NF.
- ✗
Second normal form (2NF)
Why it's wrong here
2NF requires no partial dependencies on composite keys. Since OrderID might be a single primary key, there is no partial dependency.
- ✗
First normal form (1NF)
Why it's wrong here
1NF requires atomic values, which appears satisfied; there are no repeating groups.
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