Oracle 9i Fundamentals I Exam Cram™ 2 (Exam 1Z0-031)

Column Operations

Often, you will need to perform maintenance on a table at the column level.

Dropping a Column

Designs change. It will often become apparent after a design has been implemented that some of the design assumptions were inaccurate, and a column will need to be removed from the table. In previous releases of the database, this would have been tricky, but in Oracle 9i it has been simplified. All you have to do to drop a column is ALTER the table and DROP the column:

						ALTER TABLE
						addresses
						DROP Street_addr3;
					

Dropping columns can take a significant amount of time if a significant amount of data is being deleted from the table as a result of the drop. For this same reason, dropping a column may require a significant amount of undo ...