mysql - 使用JOIN查询时出现问题

SELECT MsThread.ID, MsThread.ThreadName, Count(MsThread.ThreadName) AS TotalPost, ThreadCategory

FROM ( MsThread LEFT JOIN MsPosts ON MsThread.ThreadName = MsPosts.ThreadName )

GROUP BY MsThread.ID, MsThread.ThreadName, MsThread.ThreadCategory;

我已经检查了前面提到方括号的线程，以便加入访问工作，但是我的仍然存在此问题。

最佳答案

尝试这个：

我认为FROM语句中的括号弄乱了事情。

SELECT MsThread.ID, MsThread.ThreadName, Count(MsThread.ThreadName) AS TotalPost, ThreadCategory
FROM MsThread LEFT JOIN MsPosts ON MsThread.ThreadName = MsPosts.ThreadName
GROUP BY MsThread.ID, MsThread.ThreadName, MsThread.ThreadCategory;

或这个。可能正在寻找LEFT“ OUTER” JOIN。

SELECT MsThread.ID, MsThread.ThreadName, Count(MsThread.ThreadName) AS TotalPost, ThreadCategory
FROM MsThread LEFT OUTER JOIN MsPosts ON MsThread.ThreadName = MsPosts.ThreadName
GROUP BY MsThread.ID, MsThread.ThreadName, MsThread.ThreadCategory;