Question

使用以下查询

SELECT     evhist_XPK.event_date, evhist_XPK.zone_id, system.account
FROM         evhist_XPK INNER JOIN
             system ON evhist_XPK.system_no = system.system_no INNER JOIN
             site ON system.site_no = site.site_no INNER JOIN
             event ON event.event_id=evhist_XPK.event_id
WHERE        (evhist_XPK.event_id = '7381')  AND (evhist_XPK.event_date >= DATEADD(day, DATEDIFF(day, 1, GETDATE()), 0))
ORDER BY system.account

我明白了

event_date          zone_id     account   
2019-01-22 07:10:10.607     9           V0137C4 
2019-01-22 07:10:12.637     10          V0137C4 
2019-01-23 08:44:50.737     9           V0137C4 
2019-01-23 08:44:50.907     10          V0137C4 
2019-01-23 21:01:09.523     9           V0137C4 
2019-01-23 21:01:09.540     10          V0137C4 
2019-01-24 06:58:44.107     9           V0137C4 
2019-01-24 06:58:46.137     10           V0137C4 
2019-01-25 07:24:07.000     9           V0137C4 
2019-01-25 07:24:07.080     10          V0137C4 
2019-01-28 06:54:53.507     9           V0137C4 
2019-01-28 06:54:53.600     10          V0137C4 
2019-01-29 07:45:10.520     9           V0137C4 
2019-01-29 07:45:12.597     10          V0137C4 
2019-01-29 07:45:21.520     12          V013708 
2019-01-29 07:45:32.597     13          V013708 
2019-01-29 07:45:35.520     11          V013708 
2019-01-29 07:45:38.620     11          V013708

但是我需要获得以下这些记录，以及不同帐户的每个zone_id的最大日期时间

2019-01-29 07:45:10.520 9   V0137C4 
2019-01-29 07:45:12.597 10  V0137C4 
2019-01-29 07:45:21.520 12  V013708 
2019-01-29 07:45:32.597 13  V013708 
2019-01-29 07:45:38.620 11  V013708

Answer 1

您可以使用窗口功能。例如：

WITH q as (<your query here without the order by>)
SELECT q.*
FROM (SELECT q.*, ROW_NUMBER() OVER (PARTITION BY zone_id, account ORDER BY event_date DESC) as seqnum
      FROM q
     ) q
WHERE seqnum = 1
ORDER BY account;

或者一个有趣的方法就是简单地添加：

Answer 2

您还可以执行以下操作，这更简单：

SELECT MAX(event_date), zone_id, account
FROM
(
   --Your query
   SELECT evhist_XPK.event_date, evhist_XPK.zone_id, system.account
   FROM evhist_XPK 
   INNER JOIN system 
      ON evhist_XPK.system_no = system.system_no 
   INNER JOIN site 
      ON system.site_no = site.site_no 
   INNER JOIN event 
      ON event.event_id = evhist_XPK.event_id
   WHERE (evhist_XPK.event_id = '7381')  
   AND (evhist_XPK.event_date >= DATEADD(day, DATEDIFF(day, 1, GETDATE()), 0))
) t1
GROUP BY zone_id, account
ORDER BY account;

SQL为每个不同的zone_id选择多个最大日期，其中帐户可以相同

2 个答案: