我正在运行以下 MySQL 查询来查找没有手册的汽车(并且有黑色轮子等)
SELECT `cars`.* FROM `cars`
INNER JOIN wheels ON cars.id = wheels.car_id
LEFT OUTER JOIN manuals ON cars.id = manuals.car_id
WHERE (cars.created_at > '2010-09-09'
AND wheels.color = 'Black'
AND wheels.created_at < '2011-01-05'
AND manuals.car_id IS NULL)
查询的结果看起来是正确的,但它两次返回 id 为 27 的汽车。如何更改查询以使所有结果都是唯一的(不重复)?