Which option describes Delete Set-to-Null?

Which option describes Delete Set-to-Null?

• A. Deletes child records when the parent is deleted.
• B. Updates the foreign keys to match the old value.
• C. Prevents the deletion of the parent if referenced.
• D. When the parent is deleted, the foreign key values in child records are set to NULL.

Answer: (D)

Delete Set-to-Null tests the on delete action where removing a row from the parent table leaves the child rows intact but breaks their link to the parent by setting the referencing foreign key to NULL. This only works if the foreign key column is nullable; otherwise the delete would violate the constraint. It differs from cascade delete (which removes child rows) and from restrict/no action (which would prevent the delete if there are dependents). So the behavior described—when the parent is deleted, the foreign key values in child records are set to NULL—is exactly what this option conveys.

Delete Set-to-Null tests the on delete action where removing a row from the parent table leaves the child rows intact but breaks their link to the parent by setting the referencing foreign key to NULL. This only works if the foreign key column is nullable; otherwise the delete would violate the constraint. It differs from cascade delete (which removes child rows) and from restrict/no action (which would prevent the delete if there are dependents). So the behavior described—when the parent is deleted, the foreign key values in child records are set to NULL—is exactly what this option conveys.