SQL Query返回最后的消息

Question

示例：

我希望你理解。 我正在尝试使用此查询，但它只返回用户1发送的查询。我还需要发送给他的那些查询。但不重复相同的参与者。

Answer 1

SELECT idMsg(Max), idFrom, idTo
FROM Messages
WHERE idFrom = 1 OR idTo = 1
GROUP BY idFrom
ORDER BY visualized DESC

或

SELECT top 1 idMsg, idFrom, idTo
FROM Messages
WHERE idFrom = 1 OR idTo = 1
ORDER BY DESC

Answer 2

尝试：

SELECT idMsg, idFrom, idTo
FROM Messages
WHERE idFrom = 1 OR idTo = 1
GROUP BY idFrom
ORDER BY visualized DESC

Answer 3

我会尝试像

这样的东西

SELECT MAX(id), idto, idfrom
FROM messages
WHERE idto = 1 OR idfrom = 1
GROUP BY idto, idfrom

它可能比你需要的多一点，但它很好而且清晰。

Answer 4

尝试：

select case when idfrom < idto then idfrom else idto end userid1,
       case when idfrom > idto then idfrom else idto end userid2,
       max(id) id
from messages
where 1 in (idfrom, idto)
group by
       case when idfrom < idto then idfrom else idto end,
       case when idfrom > idto then idfrom else idto end

Answer 5

查询：

SELECT m1.idMsg, m1.idFrom, m1.idTo
FROM Messages m1
WHERE m1.dataMsg = (SELECT MAX(m2.dataMsg)
                    FROM Messages m2
                    WHERE m2.idFrom = m1.idFrom
                    AND m2.idTo = m1.idTo)