Which constraint enforces referential integrity by linking to another table's primary key?

Which constraint enforces referential integrity by linking to another table's primary key?

• A. One-to-Many Relationship
• B. Normalization
• C. Denormalization
• D. Foreign Key

Answer: (D)

The capability to enforce referential integrity by linking to another table's primary key is achieved with a foreign key constraint. A foreign key is a column (or set of columns) in one table that points to the primary key in another table. This linkage ensures that every value in the foreign key column corresponds to an existing row in the referenced table, preventing references to non-existent records. For example, an orders table with a customer_id that references customers.id guarantees that each order is linked to a real customer, and the database can enforce actions on updates or deletes (like CASCADE or SET NULL) to keep data consistent. The other concepts describe either how data relates (one-to-many relationships) or design principles (normalization and denormalization) rather than the mechanism that enforces the valid link between tables.

The capability to enforce referential integrity by linking to another table's primary key is achieved with a foreign key constraint. A foreign key is a column (or set of columns) in one table that points to the primary key in another table. This linkage ensures that every value in the foreign key column corresponds to an existing row in the referenced table, preventing references to non-existent records. For example, an orders table with a customer_id that references customers.id guarantees that each order is linked to a real customer, and the database can enforce actions on updates or deletes (like CASCADE or SET NULL) to keep data consistent.

The other concepts describe either how data relates (one-to-many relationships) or design principles (normalization and denormalization) rather than the mechanism that enforces the valid link between tables.