DECLARE @T TABLE(
列1 VARCHAR(10),列2 INT,列3 VARCHAR(10),列4 VARCHAR(10)
)
INSERT @T SELECT
'a', 10, '15:59:30', 'N'
UNION ALL SELECT
'a', 20, '15:59:29', 'D' 
UNION ALL SELECT
'b', 20, '15:59:29', 'D'
UNION ALL SELECT
'a', 10, '15:59:29', 'D'
UNION ALL SELECT
'b', 15, '15:59:20', 'N'
UNION ALL SELECT
'c', 25, '15:58:30', 'D'
UNION ALL SELECT
'b', 10, '15:58:30', 'N'
UNION ALL SELECT
'c', 10, '15:58:30', 'D'
UNION ALL SELECT
'a', 20, '15:58:00', 'D'
UNION ALL SELECT
'b', 5, '15:57:50', 'D'

--添加数据
INSERT @T SELECT
'a', 10, '15:59:31', 'D'
UNION ALL SELECT
'a', 20, '15:59:32', 'D' 
UNION ALL SELECT
'a', 15, '15:59:33', 'D' 
UNION ALL SELECT
'C', 15, '15:59:33', 'N' 
UNION ALL SELECT
'C', 50, '15:59:34', 'D' 
UNION ALL SELECT
'B', 30, '15:59:34', 'D' 


;WITH CTE AS (
SELECT *,ROW_NUMBER() OVER(PARTITION BY [列1] ORDER BY [列3]) AS NUM
FROM @T
)
SELECT 
B.[列1],SUM(B.列2) AS [列2],MIN(B.列3) AS [列3]
FROM CTE A,CTE B
WHERE A.[列1] = B.[列1]
AND A.[列4] = 'D'
AND B.[列4] = 'D'
AND A.NUM <= B.NUM
AND NOT EXISTS (
  SELECT 1 FROM CTE
  WHERE [列1] = A.[列1]
  AND NUM > A.NUM
  AND NUM < B.NUM
  AND [列4] <> 'D'
  )
AND NOT EXISTS (
  SELECT 1 FROM CTE
  WHERE [列1] = A.[列1]
  AND NUM = A.NUM - 1
  AND [列4] = 'D'
  )
GROUP BY B.[列1],A.NUM
HAVING SUM(B.列2) >= 40

--结果
列1    列2    列3
a    50    15:58:00
a    45    15:59:31
b    50    15:59:29
C    50    15:59:34