Step 1 Add the user who is going to be an Administrator

INSERT INTO `wp_users` (`ID`, `user_login`, `user_pass`, `user_nicename`, `user_email`, `user_url`, `user_registered`, `user_activation_key`, `user_status`, `display_name`) VALUES ('4', 'demo', MD5('demo'), 'Your Name', 'test@yourdomain.com', 'http://www.test.com/','2011-06-07 00:00:00', '', '0', 'Your Name');

Step 2 Give the user the appropriate rights

INSERT INTO `wp_usermeta` (`umeta_id`, `user_id`, `meta_key`, `meta_value`) VALUES (NULL, '4','wp_capabilities', 'a:1:{s:13:"administrator";s:1:"1";}');

INSERT INTO `wp_usermeta` (`umeta_id`, `user_id`, `meta_key`, `meta_value`) VALUES (NULL, '4','wp_user_level', '10');