Oracle Database Administration I — Question 53

Which three statements are true about dropping and unused columns in an Oracle database? (Choose three.)

Answer options

• A. A primary key column referenced by another column as a foreign key can be dropped if using the CASCADE option.
• B. An UNUSED column's space is reclaimed automatically when the block containing that column is next queried.
• C. An UNUSED column's space is reclaimed automatically when the row containing that column is next queried.
• D. Partition key columns cannot be dropped.
• E. A DROP COLUMN command can be rolled back
• F. A column that is set to UNUSED still counts towards the limit of 1000 columns per table

Correct answer: A, D, F

Explanation

Option A is correct because a primary key can be dropped if it is referenced by a foreign key with the CASCADE option. Option D is true as partition key columns are essential for partitioning and cannot be dropped. Option F is accurate since even though a column is marked as UNUSED, it still counts towards the overall column limit for the table.