Cálculo de diferenças de Datas

SELECT DATEDIFF(day, '2007-04-01','2007-06-04' ) AS no_of_Dias

SELECT DATEDIFF(month, '2007-04-01','2007-06-04' ) AS no_of_Meses

SELECT DATEDIFF(year, '2007-04-01','2007-06-04' ) AS no_of_Anos