SQL Server 中日期加减的方法

SELECT datediff(day,DOC_RYGL_YGDA.RZSJ,getdate()) AS day ,
datediff(month,DOC_RYGL_YGDA.RZSJ,getdate()) as month ,
datediff(year,DOC_RYGL_YGDA.RZSJ,getdate()) as year
FROM DBO.DOC_RYGL_YGDA DOC_RYGL_YGDA