Question

我正在使用Microsft SQL 2008。我需要找到前30天运行的每日最大值。这是我目前正在使用的查询以及我目前获得的示例结果。由于数据仅随着日期的增加而递增，因此我真的只需要当天的最终输入。我知道有不同的方法来获得我正在寻找的东西我只需要一些帮助就可以指明正确的方向。

SELECT HISTORY.STATION, HISTORY.NAME, HISTORY.VALUE, HISTORY.TIME
FROM DATA.dbo.HISTORY HISTORY
WHERE (HISTORY.NAME='KWMAXD') AND (HISTORY.TIME>= dateadd("Day",-30,getdate()))
ORDER BY HISTORY.TIME, HISTORY.NAME DESC



SYST    KWMAXD  49040   2013-02-24 12:59:00.000
SYST    KWMAXD  49040   2013-02-24 13:59:00.000
SYST    KWMAXD  49040   2013-02-24 14:59:00.000
SYST    KWMAXD  49040   2013-02-24 15:59:00.000
SYST    KWMAXD  49040   2013-02-24 16:59:00.000
SYST    KWMAXD  49040   2013-02-24 17:59:00.000
SYST    KWMAXD  49040   2013-02-24 18:59:00.000
SYST    KWMAXD  49040   2013-02-24 19:59:00.000
SYST    KWMAXD  49040   2013-02-24 20:59:00.000
SYST    KWMAXD  49040   2013-02-24 21:59:00.000
SYST    KWMAXD  49040   2013-02-24 22:59:00.000
SYST    KWMAXD  49040   2013-02-24 23:59:00.000
SYST    KWMAXD  28160   2013-02-25 00:59:00.000
SYST    KWMAXD  28160   2013-02-25 01:59:00.000
SYST    KWMAXD  28160   2013-02-25 02:59:00.000
SYST    KWMAXD  28160   2013-02-25 03:59:00.000
SYST    KWMAXD  28160   2013-02-25 04:59:00.000
SYST    KWMAXD  30110   2013-02-25 05:59:00.000
SYST    KWMAXD  33390   2013-02-25 06:59:00.000
SYST    KWMAXD  33390   2013-02-25 07:59:00.000
SYST    KWMAXD  33390   2013-02-25 08:59:00.000
SYST    KWMAXD  33390   2013-02-25 09:59:00.000
SYST    KWMAXD  33390   2013-02-25 10:59:00.000
SYST    KWMAXD  33390   2013-02-25 11:59:00.000
SYST    KWMAXD  33390   2013-02-25 12:59:00.000
SYST    KWMAXD  33390   2013-02-25 13:59:00.000
SYST    KWMAXD  33390   2013-02-25 14:59:00.000
SYST    KWMAXD  33390   2013-02-25 15:59:00.000
SYST    KWMAXD  36100   2013-02-25 16:59:00.000
SYST    KWMAXD  40650   2013-02-25 17:59:00.000
SYST    KWMAXD  47040   2013-02-25 18:59:00.000
SYST    KWMAXD  49650   2013-02-25 19:59:00.000
SYST    KWMAXD  49650   2013-02-25 20:59:00.000
SYST    KWMAXD  49650   2013-02-25 21:59:00.000
SYST    KWMAXD  49650   2013-02-25 22:59:00.000
SYST    KWMAXD  49650   2013-02-25 23:59:00.000
SYST    KWMAXD  43090   2013-02-26 00:59:00.000
SYST    KWMAXD  43090   2013-02-26 01:59:00.000
SYST    KWMAXD  43090   2013-02-26 02:59:00.000
SYST    KWMAXD  43600   2013-02-26 03:59:00.000
SYST    KWMAXD  45900   2013-02-26 04:59:00.000
SYST    KWMAXD  50900   2013-02-26 05:59:00.000
SYST    KWMAXD  55290   2013-02-26 06:59:00.000
SYST    KWMAXD  55290   2013-02-26 07:59:00.000
SYST    KWMAXD  55290   2013-02-26 08:59:00.000
SYST    KWMAXD  55290   2013-02-26 09:59:00.000
SYST    KWMAXD  55290   2013-02-26 10:59:00.000
SYST    KWMAXD  55290   2013-02-26 11:59:00.000

Answer 1

您应该能够使用SQL Server ranking functions，例如row_number()：

select station,
  name,
  value,
  time
from
(
  SELECT h.STATION, h.NAME, h.VALUE, h.TIME,
    row_number() over(partition by cast(h.time as date) order by h.time desc) rn
  FROM HISTORY h
  WHERE (h.NAME='KWMAXD') 
    AND (h.TIME>= dateadd(DAY,-30,cast(getdate() as date)))
) src
where rn = 1;

请参阅SQL Fiddle with Demo

如果您希望一次返回多个partition，可以将name和date扩展为name数据，因此查询将是：

select station,
  name,
  value,
  time
from
(
  SELECT h.STATION, h.NAME, h.VALUE, h.TIME,
    row_number() over(partition by h.name, cast(h.time as date) order by h.time desc) rn
  FROM HISTORY h
  WHERE (h.TIME>= dateadd(DAY,-30,cast(getdate() as date)))
) src
where rn = 1;

我需要找到前30天的每日最大值

1 个答案: