how to get number of months between 2 dates sql server

1CREATE FUNCTION FullMonthsSeparation 
2(
3    @DateA DATETIME,
4    @DateB DATETIME
5)
6RETURNS INT
7AS
8BEGIN
9    DECLARE @Result INT
10
11    DECLARE @DateX DATETIME
12    DECLARE @DateY DATETIME
13
14    IF(@DateA < @DateB)
15    BEGIN
16        SET @DateX = @DateA
17        SET @DateY = @DateB
18    END
19    ELSE
20    BEGIN
21        SET @DateX = @DateB
22        SET @DateY = @DateA
23    END
24
25    SET @Result = (
26                    SELECT 
27                    CASE 
28                        WHEN DATEPART(DAY, @DateX) > DATEPART(DAY, @DateY)
29                        THEN DATEDIFF(MONTH, @DateX, @DateY) - 1
30                        ELSE DATEDIFF(MONTH, @DateX, @DateY)
31                    END
32                    )
33
34    RETURN @Result
35END
36GO
37
38SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-05-15') as MonthSep -- =0
39SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-05-16') as MonthSep -- =1
40SELECT dbo.FullMonthsSeparation('2009-04-16', '2009-06-16') as MonthSep -- =2