一种执行所需操作的方法是使用相关子查询，以找到匹配对话的最小创建日期/时间：
SELECT m.*
FROM message m
WHERE 13 in (from_user_id, to_user_id) AND
m.created = (SELECT MAX(m2.created)
FROM message m2
WHERE (m2.from_user_id = m.from_user_id AND m2.to_user_id = m.to_user_id) OR
(m2.from_user_id = m.to_user_id AND m2.to_user_id = m.from_user_id)
)
ORDER BY m.created DESC
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