Question

我有一个表user_status，它存储每个用户的状态，每次状态更改时，我都会在user_status表中显示状态。

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

我正在寻找的是基于创建日期的每个用户的最后状态所以我看的输出是

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，我也有兴趣知道是否有办法获得每个用户的倒数第二个状态（一个在最后一个之前）状态

所以这个查询的输出我看起来是

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

Answer 1

窗口有助于救援！

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;

如果您不想要所有列，则可以使用条件聚合：

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;

Answer 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，然后转到第二个状态。希望下面的代码段有用。

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);
/

从表中获取每个用户的最新记录

2 个答案: