左连接的空结果

Question

我有一个来自mysql查询的奇怪结果：

如果我使用

SELECT cbe.id, cbe.user_id, cbe_profile_gender ,bud.status,cbe.avatar
FROM findme as cbe 
LEFT JOIN findme_buddylist as bud ON cbe.user_id = bud.userid 
WHERE cbe.user_id<>2122 
AND cbe.avatar != "" 
AND bud.status != "2"

我没有得到任何结果，因为表ade39_findme_buddylist是空的

但如果我删除该行：

AND bud.status != "2"

我得到的结果显示bud.status = NULL

有什么问题？

谢谢!!!

Answer 1

LEFT JOIN中 second 表的条件应该在in子句中：

SELECT cbe.id, cbe.user_id, cbe_profile_gender ,bud.status,cbe.avatar
FROM ade39_findme cbe LEFT JOIN
     ade39_findme_buddylist bud
     ON cbe.user_id = bud.userid and bud.status <> 2
WHERE cbe.user_id <> 2122 AND cbe.avatar <> '';