Which statement best explains referential integrity?

Question

BlackTom AI · Accepted Answer

Referential integrity requires that a foreign key value in a child table corresponds to an existing primary key value in the parent table — in other words, foreign keys must reference valid primary keys.

1) Relevant concepts
- Primary key: a column (or set of columns) whose values uniquely identify each row in a table.
- Foreign key: a column (or set of columns) in one table that refers to the primary key of another table to express a relationship.
- Referential integrity: the rule that foreign key values must either be null (if allowed) or match an existing primary key value in the referenced table; this prevents “orphan” references.
- Related constraints: entity integrity (primary keys must be unique and not null) and normalization rules (e.g., atomic attribute values).

2) Step-by-step reasoning
- Read option (a): “Foreign key values must reference valid primary keys.” This matches the textbook definition of referential integrity exactly.
- Consider option (b): “Duplicate records are prevented.” Preventing duplicates is achieved by primary key or unique constraints (entity integrity/uniqueness), not referential integrity.
- Consider option (c): “Each table must contain a primary key.” That describes entity integrity or good relational design practice, not the relationship enforcement implied by referential integrity.
- Consider option (d): “All attribute values must be atomic.” That is the First Normal Form (1NF) requirement, related to normalization, not referential integrity.

3) Intermediate logic (no numeric calculations)
- Referential integrity = rule about foreign key ↔ primary key relationships.
- Other options refer to different integrity/normalization rules.

4) Why the correct answer is correct
Option (a) directly states the constraint that enforces relationships between tables: foreign keys must point to existing primary key values. That is the essence of referential integrity and prevents orphaned child rows and inconsistent relationships.

5) Why other options are incorrect (brief)
- (b) addresses uniqueness, not references.
- (c) addresses entity integrity (primary keys), not the foreign-key-to-primary-key relationship.
- (d) addresses atomicity (normalization), unrelated to referential integrity.

Conclusion: The correct answer is (a) “Foreign key values must reference valid primary keys,” which matches the provided answer.

Which statement best explains referential integrity?单项选择题

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