MySQL中有两个左连接和一个联合

Question

我正在尝试做一个相当复杂的查询 MySQL ; 对我来说很复杂,至少.

这是我正在尝试做的一个例子:

SELECT * FROM friends
LEFT JOIN users ON users.uid = friends.fid1
LEFT JOIN users ON users.uid = friends.fid2
WHERE (friends.fid1 = 1) AND (friends.fid2 > 1)
UNION SELECT fid2 FROM friends
WHERE (friends.fid2  = 1) AND (friends.fid1 < 1)
ORDER BY RAND()
LIMIT 6;

---

我回来了:ERROR 1066 (42000): Not unique table/alias: 'users'.

我哪里出错了,我该怎么做才能真正执行这个查询？

Answer 1

别名你的表,如:

LEFT JOIN users u1 ON u1.uid = friends.fid1
LEFT JOIN users u2 ON u2.uid = friends.fid2