O post original tinha alguns bugs... então eu o reescrevi e o empacotei como um UDF.
CREATE FUNCTION FullMonthsSeparation
(
@DateA DATETIME,
@DateB DATETIME
)
RETURNS INT
AS
BEGIN
DECLARE @Result INT
DECLARE @DateX DATETIME
DECLARE @DateY DATETIME
IF(@DateA < @DateB)
BEGIN
SET @DateX = @DateA
SET @DateY = @DateB
END
ELSE
BEGIN
SET @DateX = @DateB
SET @DateY = @DateA
END
SET @Result = (
SELECT
CASE
WHEN DATEPART(DAY, @DateX) > DATEPART(DAY, @DateY)
THEN DATEDIFF(MONTH, @DateX, @DateY) - 1
ELSE DATEDIFF(MONTH, @DateX, @DateY)
END
)
RETURN @Result
END
GO
SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-05-15') as MonthSep -- =0
SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-05-16') as MonthSep -- =1
SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-06-16') as MonthSep -- =2
