当多个最大值时只选择1行

Question

我想在列A中选择最大值。现在，在列A中有多个最大值。我怎样才能用最大值取1行并将其余的关闭？我尝试使用distinct和limit 1没有成功。

预计：只有2行，1有消息“srth”，另一个有“the-same-ts-1”或“the-same-ts-2”但不是两者，因为他们有相同的最高TS 1413588888

我的查询：

SELECT A.*, DU.user as username, DU.thumbnail 
      FROM DB_CHATS A 
      INNER JOIN (
       SELECT distinct max(timestamp) TS, user, partner 
       FROM db_chats 
       GROUP BY user,partner) T 
       on A.TimeStamp=T.TS 
      and A.user=T.User 
      LEFT JOIN db_users DU on t.partner = DU.id 
where A.user = 'utQ8YDxD6kSrlI5QtFOUAE4h' 

小提琴：sqlfiddle

Answer 1

如果你不在乎已经返回该行最大时间戳，您可以添加group by user, partner, timestamp到年底你查询。

SELECT A.*, DU.user as username, DU.thumbnail 
      FROM DB_CHATS A 
      INNER JOIN (
       SELECT distinct max(timestamp) TS, user, partner 
       FROM db_chats 
       GROUP BY user,partner) T 
       on A.TimeStamp=T.TS 
      and A.user=T.User 
      LEFT JOIN db_users DU on t.partner = DU.id 
where A.user = 'utQ8YDxD6kSrlI5QtFOUAE4h' 
group by user, partner, timestamp 

http://sqlfiddle.com/#!2/efe6e/2