Question

我有以下mysql语句，我为用户选择了所有朋友。

问题是，SELECT * FROM friends WHERE (user1 = FRIEND_ID_HERE AND confirmed = 1) OR (user2 = FRIEND_ID_HERE AND confirmed = 1);中的朋友可以是user1或user2，所以我真的不知道如何加入friends table并按{members table排序1}}当我不知道哪一列包含朋友时。

我怎样才能最有效地完成这项工作？谢谢！

表格成员

last_online

表朋友

user_id | username | last_online
--------------------------------
      1 |    user1 | 1502296162
      2 |    user2 | 1502296161
      3 |    user3 | 1502296160
      4 |    user3 | 1502296159

Answer 1

我认为你需要的是这样的东西

SELECT * FROM members JOIN (
  SELECT user2 AS id FROM friends WHERE (user1 = FRIEND_ID_HERE AND confirmed = 1)
  UNION
  SELECT user1 AS id FROM friends WHERE (user2 = FRIEND_ID_HERE AND confirmed = 1)
) f ON memebers.id = f.id
ORDER BY last_online;

Answer 2

SELECT * FROM friends WHERE confirmed=1 AND friend_id_here IN (user1,user2)

MySQL选择两列中的一列匹配，另一列按列排序

2 个答案: