sql: 生日赠品中的相关算法

---2013年10月9日生日，就以2012年9月1日至2013年8月31日計算 (因為係生日月份前兩個月之最後一天為結算日)
DECLARE @birthday  datetime,@now  datetime,@stat datetime,@end datetime,@statbirthday datetime,@endbirthday datetime,@thirdbirthday datetime,@firthbirthday datetime, @year int,@month int , @day int,@str varchar(20),@total decimal
set @now=getdate()
set @year=Year(getdate())
set @birthday='1992-10-14'
set @month=month(@birthday)
set @day=day(@birthday)
set @str=cast(@year as varchar(4))+'-'+cast(@month as varchar(2))+'-'+cast(@day as varchar(2))
set @birthday=cast(@str as datetime)

--會員生日有效生首日起至3個月內有效
set @firthbirthday=DATEADD(mm, DATEDIFF(mm,0,@birthday), 0)  --当月的第一天
set @thirdbirthday=DATEADD(ms,-3,DATEADD(mm, DATEDIFF(m,0,getdate())+3, 0)) --上三个月最后的一天
set @statbirthday=DATEADD(mm, DATEDIFF(mm,0,@birthday)-13, 0)
set @endbirthday=DATEADD(ms,-3,DATEADD(mm, DATEDIFF(m,0,@birthday)-1, 0))
select @statbirthday,@endbirthday,@firthbirthday,@thirdbirthday

SELECT @total=ISNULL(SUM(amount),0) FROM View_birthdayVipdlyList WHERE indate>@statbirthday AND  indate<@endbirthday and  vipno='654321'
select @total*.01