DECLARE @YearMin INT
DECLARE @YearMax INT
DECLARE @MonthMin INT
DECLARE @MonthMax INT
DECLARE @CurrentYear INT
DECLARE @CurrentMonth INT

DECLATE @Months TABLE(DateYear INT NOT NULL, DateMonth INT NOT NULL)

SELECT @YearMin = ISNULL(MIN(YEAR(tblDetentions.DateSetFor)), YEAR(GETDATE())) FROM tblDetentions
SELECT @YearMax = ISNULL(MAX(YEAR(tblDetentions.DateSetFor)), YEAR(GETDATE())) FROM tblDetentions
SELECT @MonthMin = ISNULL(MIN(MONTH(tblDetentions.DateSetFor)), MONTH(GETDATE())) FROM tblDetentions WHERE YEAR(tblDetentions.DateSetFor) = @YearMin
SELECT @MonthMax = ISNULL(MAX(MONTH(tblDetentions.DateSetFor)), MONTH(GETDATE())) FROM tblDetentions WHERE YEAR(tblDetentions.DateSetFor) = @YearMax

SELECT @CurrentYear = @YearMin
SELECT @CurrentMonth = @MonthMin

WHILE @CurrentYear <= @YearMax
BEGIN
	WHILE (@CurrentYear < @YearMax AND @CurrentMonth <= 12) OR (@CurrentYear = @YearMax AND @CurrentMonth <= @MonthMax)
	BEGIN
		INSERT INTO @Months (DateYear, DateMonth) VALUES (@CurrentYear, @CurrentMonth)
		
		SELECT @CurrentMonth = @CurrentMonth + 1
	END
	
	SELECT @CurrentYear = @CurrentYear + 1
END

SELECT MONTH(tblMonths.DateMonth) AS MonthGiven, YEAR(tblMonths.DateYear) AS YearGiven, ISNULL(COUNT(tblDetentions.DateSetFor), 0) AS TotalDetentionsCount
FROM @Months tblMonths
INNER JOIN tblDetentions
ON MONTH(tblDetentions.DateSetFor) = tblMonths.DateMonth
AND YEAR(tblDetentions.DateSetFor) = tblMonths.DateYear
GROUP BY YEAR(tblMonths.DateYear), MONTH(tblMonths.DateMonth)
ORDER BY YEAR(tblMonths.DateYear), MONTH(tblMonths.DateMonth)