如何获得当月的天数？

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--方法一
DECLARE@monthint,@yearint
SELECT@month=6,@year=2004
SELECTDATEPART(dd,DATEADD(m,1,CAST(STR(@month)+'/01/'+STR(@year)as
datetime))-1)
--方法二
DECLARE@DATEDATETIME
SET@DATE=GETDATE()

SELECTCAST(
 --Firstdayofnextmonth
 DATEADD(MONTH,DATEDIFF(MONTH,0,@DATE)+1,0)
 -
 --Firstdayofcurrentmonth
 DATEADD(MONTH,DATEDIFF(MONTH,0,@DATE),0)
 ASINT)

--方法三
这个你也可以写一个UDF来实现：
createfunctionfn_NumOfDaysInMon(@datedatetime)
 returnsint
as
begin
declare@begmonthdatetime,@endmonthdatetime,@daysint
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
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