SqlServer計算週歲的函數

CREATE Function Dbo.GetAge
(
@birthday datetime,
@now datetime
)
Returns int
As
Begin
Declare @Age int, @year int, @month int, @Day int
Set @age = 0
Set @year = 0
Set @month = 0
Set @day = 0
Set @year = DatePart(Year,@Now) - DatePart(Year, @BirthDay)
Set @month = DatePart(Month,@Now) - DatePart(Month, @BirthDay)
Set @Day = DatePart(Day,@Now) - DatePart(Day, @BirthDay)
if( @month > 0)
Set @Age = @Year
if( @month < 0)
Set @Age = @Year - 1
if(@month = 0)
Begin
if( @Day >= 0)
Set @Age = @Year
Else
Set @Age = @Year -1
End
Return(@Age)
End