周转换日期区间，SQL函数

CREATE DEFINER=`mysqladmin`@`%` FUNCTION `convertWeekToDate`(reportYear INT,reportWeek INT) RETURNS varchar(50) CHARSET utf8
BEGIN
DECLARE str_date VARCHAR(50) DEFAULT '';
SET @dateYear = reportYear;
SET @dateWeek = reportWeek;
SET str_date = CONCAT(SUBSTRING_INDEX(str_to_date(concat(@dateYear, @dateWeek,'SUNDAY'), '%X%V%W'),'-',-2),"~",SUBSTRING_INDEX(str_to_date(concat(@dateYear, @dateWeek,'SATURDAY'), '%X%V%W'),'-',-2));
RETURN str_date;
END