oracle ocp 19c考题，科目082考试题(18)-unused column

18、Evaluate the following ALTER TABLEstatement:ALTER TABLE orders SET UNUSED (order_date);Which statement is true?A. After executing the ALTER TABLEcommand, you can add a new column called ORDER_DATE to the ORDERS table.B. The ORDER_DATE column should be empty for the ALTER TABLE command to execute succsessfully.C. ROLLBACK can be used to get back the ORDER_DATE column in the ORDERStable.D. The DESCRIBE command would still display the ORDER_DATE column.Source ： cuug