この回答では、開始日よりも後の終了日はありませんが、それがどのように機能するかを確認する必要があります。再帰的な共用体 CTE を作成し、それを使用して終了日を割り出します
CREATE TABLE #Dates
(
ID INT IDENTITY PRIMARY KEY,
START_DATE DATETIME2(0) NOT NULL,
END_DATE DATETIME2(0) NOT NULL
)
INSERT INTO #Dates VALUES ('2012-01-01', '2012-03-31'), ('2012-10-01','2012-12-31')
WITH MONTHS ([ID],[Month],[Date], [End])
AS
(
SELECT ID, DATEPART(m,START_DATE) AS [Month], START_DATE AS [Date], DATEADD(s,-1,DATEADD(m,DATEDIFF(m,0,START_DATE)+1,0)) as [End]
FROM #Dates
UNION ALL
SELECT D.ID, DATEPART(m,DATEADD(m,1,[Date])),DATEADD(m,1,[Date]), DATEADD(s,-1,DATEADD(m,DATEDIFF(m,0,DATEADD(m,1,[Date]))+1,0)) as [End]
FROM #Dates D
INNER JOIN MONTHS M
ON D.ID = M.ID
WHERE DATEADD(m,1,[Date]) < [END_DATE]
)
SELECT *
FROM MONTHS ORDER BY ID, Date
DROP TABLE #Dates