DECLARE @d DATETIME
SET @d = '23.07.1968'
SELECT
     DATEDIFF(yyyy,CAST(@d AS DATETIME),GETDATE()) 
     - 
     (CASE WHEN DATEADD(yyyy,DATEDIFF(yyyy,CAST(@d AS DATETIME),GETDATE()),CAST(@d AS DATETIME)) > 
     GETDATE() THEN 1 ELSE 0 END)

            
----------- 
35

(1 row(s) affected)