探讨如何计算age的sql函数

alter function [dbo].[get_fullage]
(
 @birthday datetime, @currentday datetime
)
returns int
as
begin
declare @age int
set @age = datediff(year, @birthday, @currentday)
if datediff(day, dateadd(year, @age, @birthday), @currentday) <= 0
 set @age = @age - 1
if datepart(month, @birthday) = 2 and datepart(day, @birthday) = 29 and datepart(month, @currentday) = 3
 and datepart(day, @currentday) = 1 and
 not (year(@currentday) % 4 = 0 and (year(@currentday) % 100 !=0 or year(@currentday) % 400 = 0))
 set @age = @age - 1
if @age < 0
 set @age = 0
  return @age
end

--sql根据出生日期计算age（不是很准确）
1.  select datediff(year,emp_birthday,getdate()) as '年龄' from  employeeunchangeinfo
2.  floor((datediff(day,u.emp_birthday,getdate()))/365