CREATE DEFINER=`root`@`%` FUNCTION `changestr`(duty_territory VARCHAR(500), location int, str VARCHAR(500)) RETURNS varchar(500) CHARSET utf8mb4
    COMMENT '替换指定字符串'
begin
        declare result varchar(500);
        declare str1 varchar(500);
        declare str2 varchar(500);
        declare num int;
        declare num1 int;
        declare num2 int;

				set num = LENGTH(duty_territory) - LENGTH( REPLACE (duty_territory, ',', ''));
				set num1 = location-1;
				set num2 = 0-(num-location+1);

				set str1 = substring_index(duty_territory,',',num1);
				set str2 = substring_index(duty_territory,',',num2);

				if LENGTH(trim(str1))=0 && LENGTH(trim(str2))=0 then
					set result = str;

				 elseif  LENGTH(trim(str1))=0 then
					set result = CONCAT(str,',',str2);

				 elseif  LENGTH(trim(str2))=0  then
					set result = CONCAT(str1,',',str);

else
					set result = CONCAT(str1,',',str,',',str2);
end if;



return result;
end