移动分组 MEDIAN / 从过去的 T-SQL 中获取特定月份的 MEDIAN

Question

假设我有一张桌子：

DATE	ID	VALUE
01.2010	1	100
02.2010	1	200
...	...	...
12.2010	1	300
01.2011	1	150
02.2011	1	250
...	...	...
12.2011	1	350
01.2012	1	200
02.2012	1	300
...	...	...
12.2012	1	400

我想获得按月分组的 VALUE 的中位数，即获得类似

DATE	ID	VALUE	MEDIAN
01.2010	1	100	100
02.2010	1	200	200
...	...	...	...
12.2010	1	300	300
01.2011	1	150	125 = (100+150)/2
02.2011	1	250	225 = (200+250)/2
...	...	...	...
12.2011	1	350	325 = (300+350)/2
01.2012	1	200	150
02.2012	1	300	250
...	...	...	...
12.2012	1	400	350

我在表格中有更多 ID，因此我想为每个 ID 获取此结果。

我试过了

SELECT PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY VALUE) OVER (PARTITION BY Id, MONTH(Date) ORDER BY Date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW)

但我得到“函数 'PERCENTILE_CONT' 可能没有窗口框架。

我也尝试了以下方法（但也没有任何结果）：

SELECT PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY VALUE)
OVER (PARTITION BY Id, MONTH(Date)) 
FROM tab1 LEFT JOIN tab2 
ON tab1.key = tab2.key
WHERE tab1.Date BETWEEN Min(Date) AND tab2.Date

编辑 到目前为止，我已经解决了

SELECT (CASE WHEN Date =2010 THEN PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY CASE WHEN Date = 2010 THEN VALUE ELSE NULL) OVER (PARTITION BY Id, MONTH(Date))  ELSE 0 END) + 
(CASE WHEN Date =2011 THEN PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY CASE WHEN Date <= 2011 THEN VALUE ELSE NULL) OVER (PARTITION BY Id, MONTH(Date))  ELSE 0 END) + 
(CASE WHEN Date =2012 THEN PERCENTILE_CONT(0.5) WITHIN GROUP (ORDER BY CASE WHEN Date <= 2012 THEN VALUE ELSE NULL) OVER (PARTITION BY Id, MONTH(Date))  ELSE 0 END)
FROM tab1

但老实说，我希望在不假设日期的先验知识的情况下做出解决方案。我考虑过 WHILE LOOP 和更新列 while @MinYear

Answer 1

我的想法是使用 (Value1+value2)/2 作为中位数，因为您的要求有点复杂。

 CREATE TABLE MedianData
  (   
  [Date] VARCHAR(100)
  ,ID INT 
  ,[Value] INT
 )

 INSERT INTO MedianData VALUES  ('01.2010', 1,  100)
    ,('02.2010',    1,  200)
    ,('12.2010',    1,  300)
    ,('01.2011',    1,  150)
    ,('02.2011',    1,  250)
    ,('12.2011',    1,  350)
    ,('01.2012',    1,  200)
    ,('02.2012',    1,  300)
    ,('12.2012',    1,  400)

 SELECT * 
       ,ROW_NUMBER() OVER  ( PARTITION BY  Substring([Date],1,2 ) ORDER BY [Date]  ) AS [row]
       ,Substring([Date],1,2 ) as [MONTH]
    INTO #Temp_tbl2
   FROM MedianData 

 SELECT
    A.Date
    ,A.ID
    ,A.[Value] 
   --Logic is applied here. I used (Value1+value2)/2 as median
   ,CASE WHEN A.[row] = 3   THEN  ( A.[Value] +  (    SELECT T.[Value] FROM #Temp_tbl2 
                    T where T.[MONTH] =  Substring(A.[Date],1,2 ) AND T.[row]  = 1 ) )/2 
    WHEN  A.[row] != 1 THEN  (A.total/2) 
    ELSE A.total END as [Median]
   INTO #Temp_table
  FROM
    (
     SELECT * 
    ,ROW_NUMBER() OVER  ( PARTITION BY  Substring([Date],1,2 ) ORDER BY [Date]  ) AS [row] 

     ,SUM ([Value] )   OVER  (  PARTITION BY  Substring([Date],1,2 ) ORDER BY [Date] ) AS [total] 
       FROM MedianData
    ) AS A

  --to make the table data order
    SELECT MedianData.*, #Temp_table.Median
    FROM MedianData
    INNER JOIN #Temp_table
         ON MedianData.[Date] =  #Temp_table.[Date] 

  drop table #Temp_table
  drop table #Temp_tbl2