内部连接语句的mysql语法错误

Question

我想从两个表中获取最后5行。

这是我执行的mysql语句：

"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"

这是错误：

  

您的SQL语法有错误;查看与您的MySQL服务器版本相对应的手册，以便在正确的语法附近使用＆＃39; ON注释AS c1 ON t1.user_id = c1.user_id WHERE t1.user_id = 1 OR c1。＆＃39;在第3行

我做错了什么？！？

Answer 1

ON之前你有一个多余的comments。

Answer 2

JOIN ON之类的内容不应只是JOIN或INNER JOIN，LEFT JOIN。像这样的东西：

"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 3

删除第3行中的额外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"