Oracle Database SQL — Question 40

Which two are true about unused columns? (Choose two.)

Answer options

• A. A query can return data from unused columns, but no DML is possible on those columns.
• B. Unused columns retain their data until they are dropped.
• C. Once a column has been set to unused, a new column with the same name can be added to the table.
• D. The DESCRIBE command displays unused columns.
• E. A primary key column cannot be set to unused.
• F. A foreign key column cannot be set to unused.

Correct answer: B, C

Explanation

Option B is correct because unused columns maintain their data until they are explicitly dropped. Option C is also correct since once a column is marked as unused, a new column with the same name can be created in the table. The other options are incorrect because they provide inaccurate information about the behavior of unused columns.