問題文
A parent row is deleted while a child table still holds rows that point at it and the statement fails. Which statement about the reference constraint explains the options?
選択肢
- The delete is rejected while no delete rule is in place and a rule can be declared so that the child rows are moved into the parent table instead.
- The delete succeeds while no delete rule is in place and the child rows are then left pointing at a value that no longer exists in the parent table at all.
- The delete is rejected while no delete rule is in place and a rule can be declared so that the child rows are removed or their reference is emptied instead.
- The delete is rejected while no delete rule is in place and the constraint has to be dropped and created again to change how the deletes behave.