如何获得当月的天数？-数据库专栏,SQL Server

–方法一
declare @month int, @year int
select @month = 6, @year = 2004
select datepart(dd,dateadd(m,1,cast(str(@month) + /01/ + str(@year) as
datetime)) – 1)
–方法二
declare @date datetime
set @date = getdate()

select cast(
 — first day of next month
 dateadd(month,datediff(month,0,@date)+1,0)
 –
 — first day of current month
 dateadd(month,datediff(month,0,@date),0)
 as int )

–方法三
这个你也可以写一个udf来实现：
create function fn_numofdaysinmon (@date datetime)
 returns int
as
begin
declare @begmonth datetime,@endmonth datetime,@days int
select @begmonth=dateadd(month,datediff(month,0,@date),0)
select @endmonth=dateadd(dd,-datepart(dd,@date),dateadd(mm,1,@date))
select @days=datediff(dd,@begmonth,@endmonth)+1
return @days
end