Mysql 获取对话的第一条消息

请帮我检索每个对话的第一条消息

表：信息

id | sender_id | recipient_id | content      | Created_at
1  | 100       | 101          | AB           | 2017-03-20 22:37:30
2  | 101       | 100          | Hello        | 2017-03-21 20:29:10
3  | 101       | 100          | XYZ          | 2017-03-21 22:02:00
4  | 200       | 100          | xxt          | 2017-03-21 23:01:01
5  | 200       | 100          | Hi there     | 2017-03-22 10:10:10
6  | 102       | 500          | Can you meet?| 2017-03-22 10:15:32
7  | 600       | 700          | Yes          | 2017-03-22 10:20:30
8  | 600       | 700          | Hello world  | 2017-03-23 01:00:00
9  | 700       | 600          | Hi           | 2017-03-23 08:10:10
10 | 800       | 900          | hello        | 2017-03-26 22:00:00

预期结果：

id | sender_id | recipient_id | content      | Created_at
1  | 100       | 101          | AB           | 2017-03-20 22:37:30
4  | 200       | 100          | xxt          | 2017-03-21 23:01:01
6  | 102       | 500          | Can you meet?| 2017-03-22 10:15:32
7  | 600       | 700          | Yes          | 2017-03-22 10:20:30
10 | 800       | 900          | hello        | 2017-03-26 22:00:00

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提前谢谢。

尝试使用带限制的相关子查询查找给定两个人之间第一次对话的id

select *
from your_table t
where id = (
        select id
        from your_table t2
        where least(t.sender_id, t.recipient_id) = least(t2.sender_id, t2.recipient_id)
            and greatest(t.sender_id, t.recipient_id) = greatest(t2.sender_id, t2.recipient_id)
        order by id limit 1
        );