Which description matches Update Restrict?

Which description matches Update Restrict?

• A. Allows a record to be updated even if its primary key is referenced by a foreign key.
• B. Deletes child records when the parent is updated.
• C. Sets all referencing keys to NULL on update.
• D. Does not allow updating a record if its primary key value is referred to by a foreign key.

Answer: (D)

Update Restrict means you cannot change the value of a primary key if that value is being referenced by a foreign key in another table. This preserves referential integrity by preventing updates that would leave child rows pointing to a key that no longer exists. In practice, the database blocks the update unless there are no dependent child rows. If you see other descriptions, they describe different referential actions. On update cascade would propagate the new key value to all child rows, not block the change. Setting the referencing keys to NULL corresponds to on-update set null, which requires the foreign key columns to be nullable. The idea of deleting child records on a parent update isn’t a standard referential action. So the description that matches Update Restrict is the one that forbids updating a record when its primary key value is referred to by a foreign key.

Update Restrict means you cannot change the value of a primary key if that value is being referenced by a foreign key in another table. This preserves referential integrity by preventing updates that would leave child rows pointing to a key that no longer exists. In practice, the database blocks the update unless there are no dependent child rows.

If you see other descriptions, they describe different referential actions. On update cascade would propagate the new key value to all child rows, not block the change. Setting the referencing keys to NULL corresponds to on-update set null, which requires the foreign key columns to be nullable. The idea of deleting child records on a parent update isn’t a standard referential action. So the description that matches Update Restrict is the one that forbids updating a record when its primary key value is referred to by a foreign key.