邮递

+-----+-----+-----+
| tid | uid | pid |
+-----+-----+-----+
|   1 |   1 |   1 |
|   2 |   1 |   2 |
|   3 |   1 |   3 |
|   3 |   2 |   4 |
|   4 |   1 |   5 |
...
+-----+-----+-----+

线

+-----+---------+---------+
| tid | lastpid | lastuid |
+-----+---------+---------+
|   1 |       0 |       0 |
|   2 |       0 |       0 |
|   3 |       0 |       0 |
|   4 |       0 |       0 |
...
+-----+---------+---------+

我希望线程的结果是：

+-----+---------+---------+
| tid | lastpid | lastuid |
+-----+---------+---------+
|   1 |       1 |       1 |
|   2 |       1 |       2 |
|   3 |       2 |       4 |
...
+-----+---------+---------+

一句话怎么说？
post's tid=thead's tid，post max（pid）的pid，uid是thead的值。
我想从post.tid eq thread.tid的post max（pid）中获取pid和uid。并将pid，uid设置为替换线程的lastpid和lastuid。
根据最佳答案，我们重写了它来解决这个问题： UPDATE thread t INNER JOIN ( SELECT tid, uid AS last_uid, pid AS last_pid FROM post WHERE pid IN (SELECT max(pid) FROM post GROUP BY tid) ) p ON t.tid = p.tid SET t.lastuid = p.last_uid, t.lastpid = p.last_pid;