GetAge

CREATE FUNCTION [dbo].[GetAge] (
	@DOB AS DATE
	,@EndDate AS DATE = NULL
	)
RETURNS TINYINT
AS
BEGIN
	DECLARE @Result AS TINYINT

	IF (@EndDate IS NULL)
		SET @EndDate = CAST(GETDATE() AS DATE)

	IF (@DOB >= @EndDate) -- trap errors
		SET @Result = 0
	ELSE
	BEGIN
		-- check if the person had its birthday in the specified year and calculate age
		IF (MONTH(@EndDate) * 100) + DAY(@EndDate) >= (MONTH(@DOB) * 100) + DAY(@DOB)
			SET @Result = CAST(DATEDIFF(Year, @DOB, @EndDate) AS TINYINT)
		ELSE
			SET @Result = CAST(DATEDIFF(Year, @DOB, @EndDate) - 1 AS TINYINT)
	END

	RETURN @Result
END