MySQL Data Types INT as AUTO_INCREMENT
Example
Any size of INT may be used for AUTO_INCREMENT. UNSIGNED is always appropriate.
Keep in mind that certain operations "burn" AUTO_INCREMENT ids. This could lead to an unexpected gap. Examples: INSERT IGNORE and REPLACE. They may preallocate an id before realizing that it won't be needed. This is expected behavior and by design in the InnoDB engine and should not discourage their use.
