分组和不工作的顺序

Question

我正在尝试分组并按顺序一起工作，但没有运气可能有人告诉我我做错了什么。

$get1_msg1 = mysqli_query($con, "select * from (select message_id, sender, receiver, message, read_status, time_sent from user_messages where receiver='".$_SESSION['userid']."' order by time_sent desc ) as temp group by sender order by time_sent desc ");

我不确定我做错了什么。

Answer 1

根据您的评论，您可以尝试

    "select message_id, sender, receiver, message, read_status, time_sent 
    from user_messages  where message_id  in (
          select message_id 
          from user_messages  
          where (sender, time_sent) in ( 
                  select  sender, max(time_sent )
                  from user_messages 
                  where receiver='".$_SESSION['userid']."' 
                  group by sender
          )
    )
    and receiver='".$_SESSION['userid']."'";