MySQL Max未选择具有多个连接的最大值

Question

我正在尝试查找我们 PBX 的从 Gradle 到坟墓报告的最新事件。我有以下代码，可以让我很好地了解每个代理今天的所有操作:

 select  e.`event_id`, `event_time` as event_time, e.g_event_id,
     p.`agent_id`,
     `a_name`, `a_number`
     from `c2g`.`events`  as e
     left join `event_parties` as p on e.`g_event_id` = p.`g_event_id`
     Left join `agent` as a on p.agent_id = a.agent_id
     where p.agent_id is not null
     and p.agent_id <> 0
     order by event_time desc;

下面的代码应该只为我提供每个代理的最新事件:

 select  e.`event_id`, MAX(`event_time`) as event_time, e.g_event_id,
    p.`agent_id`,
    `a_name`, `a_number`
    from `c2g`.`events`  as e
    left join `event_parties` as p on e.`g_event_id` = p.`g_event_id`
    Left join `agent` as a on p.agent_id = a.agent_id
    where p.agent_id is not null
    and p.agent_id <> 0
    GROUP BY a_name
    order by a_name asc;

但是我实际上并没有得到最新的事件，我得到了最近的事件，但总是有几个较新的事件被忽略。知道为什么会发生这种情况吗？

Answer 1

如果有效的话试试这个

select  e.`event_id`, e.`event_time`, e.g_event_id,
p.`agent_id`,
`a_name`, `a_number`
from `c2g`.`events`  as e
left join `event_parties` as p on e.`g_event_id` = p.`g_event_id`
Left join `agent` as a on p.agent_id = a.agent_id
where p.agent_id is not null
and p.agent_id <> 0
GROUP BY a_name
order by e.`event_time` DESC LIMIT 0,1;