--Calculate age from data of birth
USE AdventureWorks2014
GO

SELECT BirthDate, 2015-YEAR(BirthDate),
	FLOOR(DATEDIFF(DAY,BirthDate,GETDATE()) / 365) AS 'Employee''s Age',
	CASE 
		WHEN DAY(BirthDate) > DAY(GETDATE()) AND MONTH(BirthDate) >= MONTH(GETDATE())
			THEN DATEDIFF(YEAR,BirthDate,GETDATE()) - 1
		ELSE
			DATEDIFF(YEAR,BirthDate,GETDATE())
		END AS 'Employee''s Age'
FROM HumanResources.Employee