Странная сортировка

[akxxiv]

База MySQL. Структура:

CREATE TABLE `cms_site_structure` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `parent_id` int(10) unsigned NOT NULL DEFAULT '0',
  `priority` int(10) unsigned NOT NULL DEFAULT '0',
  `name` varchar(40) NOT NULL DEFAULT '',
  `uri` varchar(255) NOT NULL DEFAULT '',
  `title` varchar(100) NOT NULL DEFAULT ''
  PRIMARY KEY (`id`),
  UNIQUE KEY `uri` (`uri`),
  KEY `parent_id` (`parent_id`),
  KEY `priority` (`priority`)
) ENGINE=MyISAM  DEFAULT CHARSET=utf8;

Делаю два запроса:

SELECT 
site_structure.`uri` as `uri`,
site_structure.`title` as `title`
FROM cms_site_structure AS site_structure
WHERE
site_structure.`uri`='/' OR site_structure.`uri`='/catalogue/' OR site_structure.`uri`='/catalogue/bikes/' OR site_structure.`uri`='/catalogue/bikes/GF_Wahoo_2012/'
ORDER BY site_structure.`uri`  ASC

и

SELECT 
site_structure.`uri` as `uri`
FROM cms_site_structure AS site_structure
WHERE
site_structure.`uri`='/' OR site_structure.`uri`='/catalogue/' OR site_structure.`uri`='/catalogue/bikes/' OR site_structure.`uri`='/catalogue/bikes/GF_Wahoo_2012/'
ORDER BY site_structure.`uri`  ASC

В итоге два разных порядка сортировки:
В первом случае так ( http://joxi.ru/XAnaU4wyTJB0YxgFRMQ )

1. /
2. /catalogue/bikes/
3. /catalogue/

Во втором так ( http://joxi.ru/1QnaU4wyTJCtLrZETo0 )

1. /
2. /catalogue/
3. /catalogue/bikes/

В чем причина???