计算指定年月的最后一天的自定义MYSQL函数

/*
Name :    Fun_YiYueDeZuiHouYiTian
Function :   根据传入的格式如“200311”的年月值计算出当月的最后一天
Parameters :   
BenYue  本月
Type :  Char(6)  
Format :  "200311"
ReturnValue :   
格式如“200310”的年月值
Type :  Char(6)
Steps :
Author :   Waxdoll Cheung
Date :    2004-04-04
*/

CREATE FUNCTION dbo.Fun_YiYueDeZuiHouYiTian
(
@BenYue CHAR(6)
)
RETURNS CHAR(10)
AS
BEGIN
DECLARE @ReturnValue CHAR(2)
DECLARE @YueFen CHAR(2)
DECLARE @NianFen CHAR(4)

  SET @YueFen = RIGHT(@BenYue, 2)
SET @NianFen = LEFT(@BenYue, 4)

  IF @YueFen IN ('01', '03', '05', '07', '08', '10', '12')
BEGIN
SET @ReturnValue = '31'
END

  IF @YueFen IN ('04', '06', '09', '11')
BEGIN
SET @ReturnValue = '30'
END

  IF @YueFen = '02'
BEGIN
IF ((@NianFen % 4 = 0 AND @NianFen % 100 <> 0) OR (@NianFen % 400 = 0))
BEGIN
SET @ReturnValue = '29'
END
ELSE
BEGIN
SET @ReturnValue = '28'
END
END

  RETURN @NianFen + '-' + @YueFen + '-' + @ReturnValue
END