Dropping Constraints.

I was working on dropping a primary key constraint on a table today and when I was recreating the constraint back my create statement was failing saying that an object already exists with that name. When I checked I found that the index on the table used for the primary key was not dropped when I dropped the constraint. This I thought was a little strange. So I tried to retest why this was happening, but the next time I created and dropped the primary key constraint both the constraint and the index were dropped. When I googled for the possible cause of this kind of phenomenon I found that when the table is created in oracle 9 and we are tying to drop the constraint in oracle 10 the indexes are not dropped. To ensure that the index is also dropped below statement can be used.

alter table X drop constaint x_pk drop index;