第一张表review里有五个字段
[id],[blogid],[userid],[context],[retime]
第二张表userinfo的需要查出来的字段有两个
[username],[images]
userid存储的是第二张表的id,但是这个userid可能为空。我需要得到上面7个字段,当review.userid is null时,userinfo.username和userinfo.images就为空。我写的查询是这样的:
SELECT
[id],
[blogid],
[userid],
[username],
[context],
[retime],
[images]
FROM review,userinfo
where
review.blogid = 6
and (userinfo.id = review.userid)
or (review.userid is null)这个查询当userid不为空的情况下正常,如果userid为空的话就会把所有userinfo表里的信息也查出来。希望高手帮我指正一下。
[id],[blogid],[userid],[context],[retime]
第二张表userinfo的需要查出来的字段有两个
[username],[images]
userid存储的是第二张表的id,但是这个userid可能为空。我需要得到上面7个字段,当review.userid is null时,userinfo.username和userinfo.images就为空。我写的查询是这样的:
SELECT
[id],
[blogid],
[userid],
[username],
[context],
[retime],
[images]
FROM review,userinfo
where
review.blogid = 6
and (userinfo.id = review.userid)
or (review.userid is null)这个查询当userid不为空的情况下正常,如果userid为空的话就会把所有userinfo表里的信息也查出来。希望高手帮我指正一下。
[id],
[blogid],
[userid],
[username],
[context],
[retime],
[images]
FROM review,userinfo
where
review.blogid = 6 and ((userinfo.id = review.userid)or (review.userid is null))
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'trySELECT
[id],
[blogid],
[userid],
[username],
[context],
[retime],
[images]
FROM review,userinfo
where
review.blogid = 6
and (userinfo.id = review.userid and review.userid is not null)
or (review.userid is null)
[id],
[blogid],
[userid],
[username],
[context],
[retime],
[images]
FROM review,userinfo
where
review.blogid = 6
and (userinfo.id = review.userid and review.userid is not null)
or (review.userid is null)
[id],
[blogid],
[userid],
[username],
[context],
[retime],
[images]
FROM review
left join
userinfo
on userinfo.id = review.userid
where
review.blogid = 6