ISOWEEK的算法

算ISOWEEK的时候,通常是以(该日的所属周数+1 )- (该年的1-4所属周数),但也有特殊的情况,case1 :可能当年的一月1号到3号是属于前年的,case2 : 可能前年12月29到31号是属于下一年的.

SQL的算法

CREATE FUNCTION ISOweek (@DATE datetime)
RETURNS int
AS
BEGIN
DECLARE @ISOweek int
SET @ISOweek= DATEPART(wk,@DATE)+1
-DATEPART(wk,CAST(DATEPART(yy,@DATE) as CHAR(4))+'0104')
--Special cases: Jan 1-3 may belong to the previous year
IF (@ISOweek=0)
SET @ISOweek=dbo.ISOweek(CAST(DATEPART(yy,@DATE)-1
AS CHAR(4))+'12'+ CAST(24+DATEPART(DAY,@DATE) AS CHAR(2)))+1
--Special case: Dec 29-31 may belong to the next year
IF ((DATEPART(mm,@DATE)=12) AND
((DATEPART(dd,@DATE)-DATEPART(dw,@DATE))>= 28))
SET @ISOweek=1
RETURN(@ISOweek)
END

VB的算法

Public Function CaclISOWeek(ByVal dt As Date ) As Integer
Dim tmpd