非均匀分布式数据集的NTILE替代方案

Question

我有一个数据集并希望显示它，但它可能非常巨大（数千个点），我想过滤它们。例如，此处输出的点数为1000+：

现在我使用NTILE获得近似值，但如果点不是均匀分布的，则它不起作用。而我得到这个输出（NTILE与参数100）：

我怎样才能避免这种情况？ SQL存储过程如下：

ALTER PROCEDURE [dbo].[usp_GetSystemHealthCheckData] 
    @DateFrom datetime,   
    @DateTo datetime,    
    @EstimatedPointCount int 
    with recompile 
AS 

BEGIN 
    SET NOCOUNT ON; 
    set arithabort on 

    if @DateFrom IS NULL 
     RAISERROR ('@DateFrom cannot be NULL', 16, 1) 

    if @DateTo IS NULL 
     RAISERROR ('@DateTo cannot be NULL', 16, 1)  

    if @EstimatedPointCount IS NULL 
     RAISERROR ('@EstimatedPointCount cannot be NULL', 16, 1)  

    ;With T as 
    (
     SELECT *, GroupId = NTILE(@EstimatedPointCount) over (order by GeneratedOnUtc) 
     FROM SystemHealthCheckData 
     WHERE GeneratedOnUtc between @DateFrom AND @DateTo 
    ) 

    SELECT CpuPercentPayload = AVG(CpuPercentPayload), 
      FreeRamMb = AVG(FreeRamMb), 
      FreeDriveMb = AVG(FreeDriveMb), 
      GeneratedOnUtc = CAST(AVG(CAST(GeneratedOnUtc AS DECIMAL(18, 6))) AS DATETIME) 
    FROM T 
    GROUP BY GroupId 
END 

Answer 1

编辑：新方法

你可能会分裂与NTILE你的负载，然后计算各组的平均？我分成了4组。这让查询返回4个平均值。组的数量可以根据您拥有或可以完成修补的点数来计算。

事情是这样的：

DECLARE @tbl TABLE(id INT IDENTITY, nmbr FLOAT); 
INSERT INTO @tbl VALUES(5),(4.5),(4),(3.5),(3),(2.5),(2),(1.5),(1),(1.5),(1),(0.5),(0),(13),(2),(17),(5),(22),(24),(2),(3),(11); 

SELECT tbl2.* 
     ,AVG(nmbr) OVER(PARTITION BY tbl2.tile) 
FROM 
(
    SELECT tbl.* 
      ,NTILE(4) OVER(ORDER BY id) AS tile 
    FROM @tbl AS tbl 
)AS tbl2 

如果你想让它降低到组值仅你可以试试这个

SELECT AVG(nmbr),tbl2.tile 
FROM 
(
    SELECT tbl.* 
      ,NTILE(4) OVER(ORDER BY id) AS tile 
    FROM @tbl AS tbl 
)AS tbl2 
GROUP BY tbl2.tile 

--old文本 你也许要考虑滑动平均...在这个例子中，我尝试重建你的值（最后线性下降和野性跳跃）。您可以设置@pre和@post变量来设置“flatening”的等级。

总之：有一个平均值计算每个元素及其直接邻居。

注意的事实是，你必须添加一个ORDER BY避免随机结果...

DECLARE @tbl TABLE(id INT IDENTITY, nmbr FLOAT); 
INSERT INTO @tbl VALUES(5),(4.5),(4),(3.5),(3),(2.5),(2),(1.5),(1),(1.5),(1),(0.5),(0),(13),(2),(17),(5),(22),(24),(2),(3),(11); 

DECLARE @pre INT=3; 
DECLARE @post INT=3; 

SELECT tbl.* 
     ,AvgBorders.* 
     ,AvgSums.* 
     ,AvgSlide.* 
FROM @tbl AS tbl 
CROSS APPLY 
(
    SELECT tbl.id-@pre AS AvgStart 
      ,tbl.id + @post AS AvgEnd 
) AS AvgBorders 
CROSS APPLY 
(
    SELECT COUNT(nmbr) AS CountNmbr 
      ,SUM(nmbr) AS SumNmbr 
    FROM @tbl AS tbl 
    WHERE tbl.id BETWEEN AvgStart AND AvgEnd 
) as AvgSums 
CROSS APPLY 
(
    select AvgSums.SumNmbr/AvgSums.CountNmbr As AvgValue 
) As AvgSlide 
;