ITPEC IP April 2025 Question 28
ITPEC IP April 2025 — Question 28 of 100
EmployeeNumber — it uniquely identifies every employee and is sufficient by itself.
Condition (i) explicitly says each employee has a nonduplicated employee number, satisfying the uniqueness requirement for a primary key. EmployeeName may repeat. DepartmentCode repeats because a department has multiple employees and serves as a foreign key to the Department table, not as the Employee table's identifier.
Answer (a)
Why not others:
- (b) includes DepartmentCode unnecessarily; EmployeeNumber alone is already unique, so the composite key is not minimal
- (c) fails because employees can share a name
- (d) fails because many employees can belong to the same department
Key rule: Choose a primary key that is unique, stable, non-null, and minimal; do not add columns when one candidate key already identifies every row.
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