内部连接语句上的mysql语法错误

Question

我想从两个表中获取5个最后一行。

下面是MySQL数据库的语句我执行：

"SELECT title, thread_id 
FROM threads AS t1 
JOIN ON comments AS c1 ON t1.user_id = c1.user_id 
WHERE t1.user_id=".$userID 
." OR c1.user_id=".$userID. 
" ORDER BY thread_id DESC 
LIMIT 0,5" 

这里是错误：

您的SQL语法错误;检查对应于您的MySQL服务器版本的手册，以便在'ON注释AS c1 ON t1.user_id = c1.user_id WHERE t1.user_id = 1 OR c1'附近使用正确的语法。在线3

我在做什么错了？！？

Answer 1

在第3行删除多余的ON。它会起作用。

"SELECT title, thread_id 
FROM threads AS t1 
JOIN comments AS c1 ON t1.user_id = c1.user_id 
WHERE t1.user_id=".$userID 
." OR c1.user_id=".$userID. 
" ORDER BY thread_id DESC 
LIMIT 0,5" 

Answer 2

您在comments之前有一个多余的ON。

Answer 3

没有什么像JOIN ON应该只是JOIN或INNER JOIN,LEFT JOIN。这样的事情：

"SELECT title, thread_id 
FROM threads AS t1 
JOIN comments AS c1 ON t1.user_id = c1.user_id 
WHERE t1.user_id=".$userID 
." OR c1.user_id=".$userID. 
" ORDER BY thread_id DESC 
LIMIT 0,5"