更新时间:2023-10-06 11:36:40
将条件指定为ON子句的一部分:
Specify the condition as part of the ON clause:
SELECT m.id, u.first_name AS otherUser
FROM matches AS m
LEFT JOIN users AS u ON (u.id=m.user2ID and u.id = m.user1ID) or (u.id<>m.user2ID and u.id = m.user2ID)
WHERE m.user1ID=2 OR m.user2ID=2
做同样事情的另一种方法:
Another way to do the same thing:
SELECT m.id, u.first_name AS otherUser
FROM matches AS m
LEFT JOIN users AS u ON IF(u.id=m.user2ID,u.id = m.user1ID,u.id = m.user2ID)
WHERE m.user1ID=2 OR m.user2ID=2