累积计数超过日期，丢弃一些值

Question

我有以下架构的答案表：

CREATE TABLE Answers 
    ([id] int, [analyst_id] int, [date] date); 

我要“累积计数”的分析师每月有多少答案了，丢弃前给出任何答案最后一个答案后的3个月。鉴于以下几点：

INSERT INTO Answers 
    ([id], [analyst_id], [date]) 
VALUES 
    (1, 1, '2017/01/01'), 
    (2, 1, '2017/02/01'), -- should be discarded 
    (3, 1, '2017/03/01'), -- should be discarded 
    (4, 1, '2017/05/01'), 
    (5, 1, '2017/06/01'), -- should be discarded 
    (6, 1, '2017/07/01'), -- should be discarded 
    (7, 1, '2017/08/01'), 
    (8, 2, '2017/01/01'), 
    (9, 2, '2017/04/01'), 
    (10, 1, '2018/02/01'), 
    (11, 2, '2018/03/01'); 

预期的结果是：

analyst_id | month-year | count 
------------------------------- 
1   | 01/2017 | 1 
1   | 02/2017 | 1 
1   | 03/2017 | 1 
1   | 04/2017 | 1 
1   | 05/2017 | 2 
1   | 06/2017 | 2 
1   | 07/2017 | 2 
1   | 08/2017 | 3 
1   | 09/2017 | 3 
1   | 10/2017 | 3 
1   | 11/2017 | 3 
1   | 12/2017 | 3 
2   | 01/2017 | 1 
2   | 02/2017 | 1 
2   | 03/2017 | 1 
2   | 04/2017 | 2 
2   | 05/2017 | 2 
2   | 06/2017 | 2 
2   | 07/2017 | 2 
2   | 08/2017 | 2 
2   | 09/2017 | 2 
2   | 10/2017 | 2 
2   | 11/2017 | 2 
2   | 12/2017 | 2 
1   | 01/2018 | 0 
1   | 02/2018 | 1 
1   | 03/2018 | 1 
2   | 01/2018 | 0 
2   | 02/2018 | 0 
2   | 03/2018 | 1 

DBMS是SQL Server 2012

编辑

我写这拨弄着我目前的半解决方案：http://sqlfiddle.com/#!6/c2e82e/5

每年，计数需要重置。

Answer 1

编辑：

OK，对于更新的问题，你实际上需要做的是包含了所有的最小和最大日期之间的日期的“日期”表（这里的CTE称为“d”）你的答案表。然后，您可以基本上将结果加入到结果中，并使用窗口函数确定计数。

DECLARE @Answers TABLE (ID INT, Analyst_ID INT, [Date] DATE); 
INSERT @Answers (ID, Analyst_ID, [Date]) 
VALUES 
    (1, 1, '2017/01/01'), 
    (2, 1, '2017/02/01'), 
    (3, 1, '2017/03/01'), 
    (4, 1, '2017/05/01'), 
    (5, 1, '2017/06/01'), 
    (6, 1, '2017/07/01'), 
    (7, 1, '2017/08/01'), 
    (8, 2, '2017/01/01'), 
    (9, 2, '2017/04/01'), 
    (10, 1, '2018/02/01'), 
    (11, 2, '2018/03/01'); 

WITH CTE AS 
(
    SELECT A.Analyst_ID, [Date] = MIN(A.[Date]) 
    FROM @Answers AS A 
    GROUP BY A.Analyst_ID 
    UNION ALL 
    SELECT A.Analyst_ID, A.[Date] 
    FROM 
    (
     SELECT A.Analyst_ID, A.[Date], RN = ROW_NUMBER() OVER (PARTITION BY A.Analyst_ID ORDER BY A.ID) 
     FROM @Answers AS A 
     JOIN CTE 
      ON CTE.Analyst_ID = A.Analyst_ID 
      AND DATEADD(MONTH, 3, CTE.[Date]) <= A.[Date] 
    ) AS A 
    WHERE A.RN = 1 
), 

D AS -- List of dates between minimum and maximum date in table for each analyst ID. 
(
    SELECT [Date] = DATEADD(MONTH, RN, (SELECT MIN([Date]) FROM @Answers)), 
      A.Analyst_ID 
    FROM (SELECT RN = ROW_NUMBER() OVER (ORDER BY (SELECT NULL)) - 1 FROM sys.objects) AS O 
    CROSS JOIN (SELECT DISTINCT Analyst_ID FROM @Answers) AS A 
    WHERE RN <= (SELECT DATEDIFF(MONTH, MIN([Date]), MAX([Date])) FROM @Answers) 
) 

SELECT D.Analyst_ID, 
     [Month-Year] = FORMAT(D.[Date], 'MM/yyyy'), 
     [Count] = CASE WHEN A.[Date] IS NULL THEN 0 ELSE DENSE_RANK() OVER (PARTITION BY D.Analyst_ID, DATEPART(YEAR, A.[Date]) ORDER BY A.[Date]) END 
FROM D 
OUTER APPLY (SELECT TOP 1 * FROM CTE WHERE CTE.[Date] <= D.[Date] AND DATEDIFF(YEAR, CTE.[Date], D.[Date]) = 0 AND CTE.Analyst_ID = D.Analyst_ID ORDER BY CTE.[Date] DESC) AS A 
ORDER BY D.Analyst_ID, D.[Date];