select PostComment.PostID from PostComment join CommentReply on PostComment.UserID=CommentReply.UserID where CommentReply.UserID=1 or PostComment.UserID=1

就如图那样的结果怎么让他 postID 1 4 5 7 只显示一次啊

就像本论坛的 查询我参与过的主题一样

distinct

能不能写个整句的来看看

SELECT DISTINCT PostComment.PostID
FROM PostComment JOIN
     CommentReply ON PostComment.UserID=CommentReply.UserID
WHERE CommentReply.UserID=1 OR
      PostComment.UserID=1
ORDER BY PostComment.PostID

查询 UserID =2 所参与过的帖子 明明就有啊 post=4 的就啊他参与过的
但是这句：
select distinct PostComment.PostID
from PostComment JOIN
     CommentReply on PostComment.UserID=CommentReply.UserID
where PostComment.UserID=2  or
      CommentReply.UserID=2
却没有查出来


这是为什么啊？急啊  求解