从表中获取每个用户的最新记录[重复]答案

【问题标题】：get the latest record from the table for each user [duplicate]从表中获取每个用户的最新记录[重复]
【发布时间】：2017-08-20 23:24:06
【问题描述】：

我有一个 user_status 表，它存储每个用户的状态，每次状态更改时，我都会在 user_status 表中添加状态。

id   status     created 
1    ACTIVE     08-10-2017 08:21:22
1    ACTIVE     08-10-2017 08:21:25
1    NON_ACTIVE 08-10-2017 08:22:23
2    NON_ACTIVE 08-10-2017 08:22:23
2    ACTIVE     08-11-2017 08:25:23
3    NON_ACTIVE 08-12-2017 08:23:23

我要查找的是基于创建日期的每个用户的最后状态所以我正在寻找的输出是

id   status     created 
1    NON_ACTIVE 08-10-2017 08:22:23
2    ACTIVE     08-11-2017 08:25:23
3    NON_ACTIVE 08-12-2017 08:23:23

一旦我这样做了，我也很想知道是否有办法为每个用户获取倒数第二个状态（最后一个）状态

所以我正在寻找的这个查询的输出是

1    ACTIVE     08-10-2017 08:21:25
2    NON_ACTIVE 08-10-2017 08:22:23
3    NON_ACTIVE 08-12-2017 08:23:23

任何建议，我

【问题讨论】：

标签： sql oracle oracle11g greatest-n-per-group

【解决方案1】：

拯救窗口函数！

select t.*
from (select t.*,
             row_number() over (partition by id order by created desc) as seqnum,
             nth_value(status, 2) over (partition by id order by created desc) as second_status
      from t
     ) t
where seqnum = 1;

如果不想要所有列，可以使用条件聚合：

select t.id, max(t.created) as created,
       max(case when seqnum = 1 then status end) as last_status,
       max(case when seqnum = 2 then status end) as second_status,
from (select t.*,
             row_number() over (partition by id order by created desc) as seqnum
      from t
     ) t
group by id;

【讨论】：

有什么理由匿名否决看似正确的答案？
我不确定是谁投了反对票，我仍在调查您的问题。我不确定谁投了反对票
@user641887 。 . .它看起来像一个恶意的投反对票者，他只是对问题和所有答案投了反对票。
@GordonLinoff 给了你一票；）

【解决方案2】：

查看您的查询，我建议一次性获取详细信息，而不是获取第一个状态然后再进行第二个状态。希望下面的 sn-p 有所帮助。

SELECT B.ID,
  B.STATUS,
  B.CREATED
FROM
  (SELECT A.ID,
    A.STATUS,
    CREATED,
    ROW_NUMBER() OVER(PARTITION BY A.ID ORDER BY A.CREATED DESC) RN
  FROM
    (SELECT 1 ID,'ACTIVE' STATUS,'08-10-2017 08:21:22' CREATED FROM DUAL
    UNION ALL
    SELECT 1 ID,'ACTIVE' STATUS,'08-10-2017 08:21:25' CREATED FROM DUAL
    UNION ALL
    SELECT 1 ID,'NON_ACTIVE' STATUS,'08-10-2017 08:22:23' CREATED FROM DUAL
    UNION ALL
    SELECT 2 ID,'NON_ACTIVE' STATUS,'08-10-2017 08:22:23' CREATED FROM DUAL
    UNION ALL
    SELECT 2 ID,'ACTIVE' STATUS,'08-11-2017 08:25:23' CREATED FROM DUAL
    UNION ALL
    SELECT 3 ID,'NON_ACTIVE' STATUS,'08-12-2017 08:23:23' CREATED FROM DUAL
    )A
  )B
WHERE B.RN IN (1,2);
/

【讨论】：