Aká chyba?

V mysql mi píše chybu aká je chyba?

Chyba
SQL dopyt:

CREATE TABLE `uzivatele` (

`id_uzivatele` MEDIUMINT( 8 ) UNSIGNED NULL AUTO_INCREMENT ,
`uziv_jmeno` VARCHAR( 20 ) NULL ,
`jmeno` VARCHAR( 15 ) NOT NULL ,
`prijmeni` VARCHAR( 30 ) NOT NULL ,
`email` VARCHAR( 40 ) NULL ,
`heslo` VARCHAR( 16 ) NOT NULL ,
`datum_registrace` DATETIME NOT NULL
) ENGINE = MYISAM

MySQL hlási:

#1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key

Díky už to ide. :)