我有三张桌子A B C,我试图从这三张桌子中检索信息。
A具有columnns userid头像用户名,B具有postid列,dateshared和C具有postid datecommented的列评论者。
我试图运行查询
Select C.comment, C.commenter, C.datecommented, B.postid, B.dateshared A.username A.avatar from B Left Join C Left join A on C.postid = B.postid AND A.userid = C.commenter where B.postid IN ('1','2','3') order by C.dateshared desc
但它会出现以下错误:
You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'where B.postid IN ('1', '2', '3') order by C.dateshared '
任何人都可以指出我做错了什么或建议怎么做吗?
答案 0 :(得分:2)
每个LEFT JOIN
都需要自己的ON
条件:
SELECT C.comment, C.commenter, C.datecommented, B.postid, B.dateshared, A.username A.avatar
FROM B
LEFT JOIN
C
ON C.postid = B.postid
LEFT JOIN
A
ON A.userid = C.commenter
WHERE B.postid IN ('1','2','3')
ORDER BY
C.dateshared desc
答案 1 :(得分:0)
我在您的示例查询中看到了几个问题:
我会将其重写为:
SELECT C.comment, C.commenter, C.datecommented, B.postid, B.dateshared, A.username, A.avatar
FROM B
LEFT JOIN C ON C.postid = B.postid
LEFT JOIN A ON A.userid = C.commenter
WHERE B.postid IN ('1','2','3')
ORDER BY C.dateshared desc
答案 2 :(得分:0)
这应该适合您,您的查询有一些语法错误:
Select C.comment,C.commenter,C.datecommented,B.postid,B.dateshared,A.username,A.avatar
from B
Left Join C on C.postid = B.postid
Left join A on A.userid = C.commenter
where B.postid IN ('1','2','3')
order by C.dateshared desc