mysql - 3 个表的内部联接如何获取日期最大值的 Id？

Question

这是我的查询:

SELECT CON_ID, CON_CreatedBy, COM_DateTime FROM CON_Conversation
    INNER JOIN COU_ConversationUser AS cu USING (CON_ID)
    INNER JOIN COM_ConversationMessage AS cm USING (CON_ID)
WHERE cu.USR_ID = 4328 AND cm.USR_ID = 4328
ORDER BY CON_ID DESC

这是我的结果:

现在我只想返回具有 MAX COM_DateTime 的 CON_Id。 我该怎么做？？

Answer 1

子选择应该适合你:

select CON_ID, max(COM_DateTime)
from
(
    SELECT CON_ID, COM_DateTime 
    FROM CON_Conversation
    INNER JOIN COU_ConversationUser AS cu USING (CON_ID)
    INNER JOIN COM_ConversationMessage AS cm USING (CON_ID)
    WHERE cu.USR_ID = 4328 AND cm.USR_ID = 4328
    ORDER BY CON_ID DESC
) as sub
group by CON_ID
ORDER BY max(COM_DateTime) DESC