You execute this command:ALTER TABLE employees SET UNUSED (department_id);Which two are true?

D. True, after setting the DEPARTMENT_ID column to UNUSED, you can add a new column with the name DEPARTMENT_ID to the EMPLOYEES table. The UNUSED clause does not delete the column, it only marks it as no longer being used.E. True, once a column is marked as UNUSED, you cannot make updates to it. It becomes inaccessible for DML operations.

A, B, C, and F are not correct because: A. Once a column is set to UNUSED, it is not available for queries. B. The storage space is not immediately released after issuing a COMMIT; instead, the actual removal and space reclamation happen when you subsequently issue the DROP UNUSED COLUMNS operation. C. The DEPARTMENT_ID column is not set to null; instead, it's marked as UNUSED, which means it is no longer available for use. F. UNUSED columns are not placed into the recycle bin; they are just marked for deletion, and space can be reclaimed with the DROP UNUSED COLUMNS command.

References:

Oracle documentation on ALTER TABLE: Oracle Database SQL Language Reference

Understanding ALTER TABLE SET UNUSED: Oracle Database Administrator’s Guide