第一步：编写判断一年是否是闰年的函数IsLeapYear

<strong>CREATE FUNCTION IsLeapYear( @Year  INT)
RETURNS BIT AS  
BEGIN IF (@Year % 4 = 0) and ((@Year % 100 <> 0) or (@Year % 400 = 0))  RETURN 1 RETURN 0
END</strong>

第二步：编写一年中每个月的天数函数DaysPerMonth

CREATE FUNCTION DaysPerMonth( @Year INT, @Month INT)
RETURNS INT AS  
BEGIN declare @Days INTSET @Days =case @Monthwhen 1 then 31when 2 then 28when 3 then 31when 4 then 30when 5 then 31when 6 then 30when 7 then 31when 8 then 31when 9 then 30when 10 then 31when 11 then 30else 31endIF (@Month = 2) and (dbo.IsLeapYear(@Year) =1)--调用第一步的闰年判断函数。SET @Days= @Days +1return @Days
END