Question

Which rule states that no two records can have the same primary key?

• A. Key integrity
• B. Referential integrity
• C. Key uniqueness
• D. Domain integrity

Hint:

Remember: \[ \boxed{ \text{Primary Key} \rightarrow \text{Unique for every record} } \] Duplicate primary keys are never allowed.

Answer 1

The Correct Option is C

Concept: A primary key uniquely identifies each record in a database table. The Key Uniqueness rule ensures that no two records share the same primary key value.

Step 1: Recall database constraints.
• Key uniqueness $\rightarrow$ No duplicate primary keys.
• Referential integrity $\rightarrow$ Valid foreign key relationships.
• Domain integrity $\rightarrow$ Valid attribute values.

Step 2: Identify the correct rule. Thus, \[ \boxed{\text{Key uniqueness ensures every primary key is unique}.} \] Therefore, the correct option is \[ \boxed{(C).} \]