SQL Index Performance - ASC vs DESC

Question

I\'ve got a user table keyed on an auto-increment int column that looks something like this:

CREATE TABLE `user_def` (
  `user_id` int(11) NOT NULL AUTO_INC         


        

Answer 1

In MySQL defining ASC or DESC for indexes is not only unsupported, but it would also be pointless. MySQL can traverse indexes in both directions as needed, so it does not require the order to be defined explicitly.