RENAME FAQS

1. How can I rename a comment in Oracle?

In Oracle, there is no direct RENAME COMMENT command. To "rename" a comment, you need to drop the old comment by setting it to NULL and then add a new comment using the COMMENT ON statement.

2. How do I drop a comment in Oracle?

To drop a comment in Oracle, use the COMMENT ON statement with IS NULL:

COMMENT ON <object_type> <object_name> IS NULL;

For example, to drop a comment on a table named employees:

COMMENT ON TABLE employees IS NULL;

3. How do I add a new comment after dropping the old one?

After dropping the old comment, you can add a new comment using:

COMMENT ON <object_type> <object_name> IS 'New comment text';

For example, to add a new comment on the employees table:

COMMENT ON TABLE employees IS 'This table stores employee details such as name, position, and salary.';

4. Can I rename a comment for a column in a table?

Yes, you can rename a comment for a column by first dropping the old comment and then adding the new one. For example:

COMMENT ON COLUMN employees.salary IS NULL;  -- Drop the old comment

COMMENT ON COLUMN employees.salary IS 'Updated employee salary details for the year 2025.';  -- Add the new comment

5. How can I view the current comments before renaming them?

You can view existing comments using the following queries:

·        For tables:

·        SELECT table_name, comments

·        FROM user_tab_comments

·        WHERE table_name = 'YOUR_TABLE_NAME';

·        For columns:

·        SELECT table_name, column_name, comments

·        FROM user_col_comments

·        WHERE table_name = 'YOUR_TABLE_NAME';

·        For views:

·        SELECT view_name, comments

·        FROM user_view_comments

·        WHERE view_name = 'YOUR_VIEW_NAME';

·        For indexes:

·        SELECT index_name, comments

·        FROM user_index_comments

·        WHERE index_name = 'YOUR_INDEX_NAME';

6. Is there a limit on comment length in Oracle?

Yes, comments in Oracle can be up to 4000 characters in length.

7. Can I track changes to comments in Oracle?

Oracle does not natively track changes to comments. If you need to track changes, you would need to implement external auditing solutions or manually document comment changes.

8. Does renaming a comment affect the object itself?

No, renaming a comment (by dropping and adding a new one) does not affect the functionality or data of the object. It only changes the description associated with that object.

9. Can I rename a comment for database objects other than tables and columns?

Yes, you can rename comments for views, indexes, sequences, and other objects by following the same method: drop the existing comment and add the new one.

10. What happens if I drop an object that has a comment?

If you drop an object (such as a table, column, or index), its associated comment is automatically removed. However, you can manually drop the comment before dropping the object if needed.

11. Are comments stored in the Oracle data dictionary?

Yes, comments are stored in Oracle’s data dictionary views, such as user_tab_comments for tables and user_col_comments for columns.

12. Can I rename multiple comments at once?

Oracle does not support renaming multiple comments at once. You must drop and add each comment individually for each object.

13. Can I rename a comment for a sequence?

Yes, you can rename a comment for a sequence by first dropping the existing comment and then adding a new one:

COMMENT ON SEQUENCE seq_name IS NULL;  -- Drop the old comment

COMMENT ON SEQUENCE seq_name IS 'New description for the sequence';  -- Add the new comment

14. Can I use RENAME command to change the comment?

No, the RENAME command in Oracle is used to rename objects like tables, columns, views, etc. It cannot be used to rename comments. You have to use the COMMENT ON statement to remove the old comment and add a new one.