Question

我有一张五年的数据表。除其他值外，它还有JulianDate，RefETo和Precipitation。

我需要获得五年内RefETo的平均值和去年的平均值，加上去年的降水量之和。

同时，平均值和总和必须持续7到28天。

现在，我正在使用一个函数：

FUNCTION [dbo].[CIMISAvg](@Stn INT, @Yr INT,  @Period INT)
RETURNS @AvgTable TABLE (Period INT, RefETo float, RefETo1 float, Precipitation float)
AS
BEGIN
    DECLARE @PeriodInc INT = 1
    DECLARE @RefETo float
    DECLARE @Precip float
    DECLARE @RefETo1 float
    DECLARE @P INT = 1
    BEGIN
        WHILE @PeriodInc < 366
           BEGIN
              IF @PeriodInc < 365
                 BEGIN
                    SET @RefETo = (SELECT AVG(RefETo) FROM Cimis 
                     WHERE StationNo = @Stn AND RefETO >= 0 AND JulianDate BETWEEN @PeriodINC AND 
                     PeriodINC + @Period - 1)
                    SET @RefETo1 = (SELECT AVG(RefETo) FROM Cimis WHERE StationNo = @Stn AND 
                     RefETO >= 0 AND JulianDate BETWEEN @PeriodINC AND @PeriodINC + @Period - 1 
                     AND DATEPART(Year, DateCollected) = @Yr)
                    SET @Precip = (SELECT SUM(Precipitation) FROM Cimis 
                     WHERE StationNo = @Stn AND Precipitation >= 0 AND JulianDate 
                     BETWEEN @PeriodINC AND @PeriodINC + @Period - 1 
                     AND DATEPART(Year, DateCollected) = @Yr)
                 END
              ELSE
                 BEGIN
                    SET @RefETo = (SELECT AVG(RefETo) FROM Cimis 
                     WHERE StationNo = @Stn AND RefETO >= 0 
                     AND (JulianDate > 364 OR JulianDate < @Period - 1))                        
                    SET @RefETo1 = (SELECT AVG(RefETo) FROM Cimis WHERE StationNo = @Stn 
                     AND RefETO >= 0  AND JulianDate > 364 
                     AND DATEPART(Year, DateCollected) = @Yr)
                    SET @Precip = (SELECT SUM(Precipitation) FROM Cimis WHERE StationNo = @Stn 
                     AND Precipitation >= 0 AND JulianDate > 364 
                     AND DATEPART(Year, DateCollected) = @Yr)
                 END
              INSERT INTO @AvgTable(Period, RefETo, RefETo1, Precipitation) 
              VALUES (@P, @RefETo, @RefETo1, @Precip)
              SET @PeriodInc += @Period
              SET @P += 1
           END
        END
   RETURN
END

如果我使用，则返回下表：

SELECT * from dbo.CimiAvg(80,2014,28)

Period RefETo                RefETo1               Precipitation
1      0.0417192857142857    0.0470392857142857    0.0156
2      0.0672328571428571    0.0585214285714286    0
3      0.121372142857143     0.135967857142857     1.2755
4      0.170277519379845     0.186428571428571     0.7991
5      0.235207258064516     0.240425              0.7087
6      0.268260240963855     0.294403571428571     0.1811
7      0.293128125           0.290282142857143     0
8      0.273767123287671     0.267457142857143     0.0196
9      0.244358333333333     0.2513375             0
10     0.176087142857143     NULL                  NULL
11     0.10749               NULL                  NULL
12     0.0625579831932773    NULL                  NULL
13     0.0382158273381295    NULL                  NULL
14     0.0413401459854015    NULL                  NULL

哪个好，花花公子，但有没有人有更好的想法？

我已经摆弄

了

SELECT JulianDate, AVG(RefETO) 
                   OVER (ORDER BY JulianDate ROWS BETWEEN 28 PRECEDING AND CURRENT ROW) 
FROM Cimis

并且有各种各样的变化但是没有任何地方

Answer 1

我同意评论中的PM 77-1。条件聚合是可行的方法。

试试这个：

Declare @Stn INT, @Yr INT,  @Period INT
Select @Stn = 80, @Yr=2014, @Period=28

SELECT Period, RefETo/RefEToDays AS RefETo, RefETo1/RefETo1Days AS RefETo1, Precipitation
FROM    (
    SELECT 
    ROUNDUP(JulianDate/@Period,0) AS Period,
    SUM(
      RefETo
    ) AS RefETo,
    SUM(
        CASE WHEN DATEPART(Year, DateCollected) = @Yr  THEN RefETo ELSE 0 END
    ) AS RefETo1,
    COUNT(*)
      AS RefEToDays,
    SUM(
        CASE WHEN DATEPART(Year, DateCollected) = @Yr THEN 1 ELSE 0 END
    ) AS RefETo1Days,
    SUM(
        CASE WHEN DATEPART(Year, DateCollected) = @Yr Then Precipitation ELSE 0 END
    ) AS Precipitation
    FROM Cimis
    WHERE StationNo = @Stn 
    GROUP BY ROUNDUP(JulianDate/@Period,0)
    ) c

Answer 2

我需要在五年内获得RefETo的平均值去年的平均值加上去年的降水量之和年。

从我所处的位置来看，这是一个应该在报表编写器中实现的需求的完美示例，而不是在dbms中。

我不会在单个SQL语句中执行此操作。

Answer 3

是的！为此，肯定有更好的，更有表现力的手段。

首先要确保您在数据库中定义了NUMBERS table，或者熟悉如何使用CTE动态生成一个（公用表表达式）：

主查询现在变为：

DECLARE @NumPeriods as INT = 365 / @Period;

WITH
    -- vvv BEGIN Needed only in absence of a NUMBERS table
    E1(N) as (
        SELECT 1 FROM (VALUES  (1),(1),(1),(1),(1),(1),(1),(1),(1),(1)  )E1(N)
    ),
    E2(N) as ( SELECT 1 FROM E1 a CROSS JOIN E1 b ),
    E4(N) as ( SELECT 1 FROM E2 a CROSS JOIN E2 b ),
      -- repeated for E8, E16, as needed
    -- ^^^ END Needed only in absence of a NUMBERS table

Tally(N) as (
    SELECT TOP(@NumPeriods) -- This is sufficient for our purposes 
        ROW_NUMBER() OVER (ORDER BY N) AS N 
    FROM E4
    UNION ALL
    SELECT 0
)
INSERT INTO @AvgTable(Period, RefETo, RefETo1, Precipitation) 
    SELECT
         p.Period
        ,AVG(RefETo) as RefETo
        ,SUM(case when DATEPART(Year, DateCollected) = @yr then RefETo else 0 end)
        /SUM(case when DATEPART(Year, DateCollected) = @yr then    1   else 0 end) 
                     as RefETo1
        ,SUM(case when DATEPART(Year, DateCollected) = @yr then Precipitation 
                                                           else 0 end)
                     as Precipitation
    FROM Cimis
    JOIN (
        SELECT
             N, N + 1           as Period
            ,(N*@Period) + 1 as StartDate
            ,CASE WHEN N * @Period > 363 THEN @Period - 1 ELSE (N + 1) * @Period END AS EndDate

        FROM Tally
    ) p
       ON JulianDate BETWEEN p.StartDate AND p.EndDate 
       OR ((JulianDate > 364 OR JulianDate < @Period - 1) AND p.N * @Period > 363)

    WHERE StationNo  = @Stn
      AND RefETO    >= 0 
    GROUP BY  p.Period
    PRDER BY  p.Period

我相信您会发现这种实现在大型数据集上要比当前实现快得多。

Answer 4

我认为这是基于Jim V代码的最终版本。最后一个时期由UNION处理。

DECLARE @Stn INT, @Yr INT,  @Period INT
SELECT @Stn = 80, @Yr=2014, @Period=28

SELECT Period, RefETo, RefETo1, Precipitation
FROM (
SELECT CEILING(JulianDate / @Period) AS Period, AVG(RefETo) AS RefETo, 
AVG(CASE WHEN DATEPART(Year, DateCollected) = @Yr THEN RefETo ELSE NULL END) AS RefETo1, 
SUM(CASE WHEN DATEPART(Year, DateCollected) = @Yr Then Precipitation ELSE 0 END) AS
Precipitation 
FROM Cimis WHERE StationNo = @Stn AND JulianDate < 365
GROUP BY CEILING(JulianDate / @Period)) C
UNION SELECT 366 / @Period + 1 AS Period, AVG(RefETo) AS RefETo, 
(SELECT AVG(RefETo) FROM CIMIS 
WHERE DATEPART(Year, DateCollected) = @Yr AND JulianDate > 364) AS RefETo1,
(SELECT SUM(Precipitation) FROM CIMIS 
WHERE DATEPART(Year, DateCollected) = @Yr AND JulianDate > 364) AS Precipitation 
FROM Cimis WHERE StationNo = @Stn AND (JulianDate > 364 OR JulianDate < @Period - 1) 
ORDER BY Period

一种在一段时间内获得平均值的方法

4 个答案: