SQL检索每个threadID的最新记录

Question

表结构：

id | sender | receiver | subject | message | threadID | timestamp | date | readStatus

SELECT * FROM mail 
WHERE sender = 'redphyre' OR receiver = 'redphyre' 
AND threadID BETWEEN (select min(threadID) FROM mail WHERE sender = 'redphyre' OR receiver = 'redphyre' ORDER BY id DESC) 
AND (select max(threadID) FROM mail WHERE sender = 'redphyre' OR receiver = 'redphyre' ORDER BY id DESC) 
GROUP BY threadID;

在此情况下，我试图获取每个用户redphyre的用户threadID的最新记录，在本例中为threadID的0,1,2。但这不是那样的。取而代之的是，我在threadID之间得到了混合结果。有人有什么想法吗？

Answer 1

大概是您想要的：

SELECT m.*
FROM mail m
WHERE 'redphyre' IN (m.sender, m.receiver) AND
      m.id = (SELECT MAX(m2.id)
              FROM mail m2
              WHERE 'redphyre' IN (m2.sender, m2.receiver) AND m2.threadID = m.threadID
             );

BETWEEN和GROUP BY确实与您想要的内容无关。子查询会考虑同一线程上的所有匹配记录，并返回具有最大id的记录。