select query error

[cnu sri]

DELIMITER $$

DROP PROCEDURE IF EXISTS `yo31`.`GetFriends`$$

CREATE DEFINER=`root`@`localhost` PROCEDURE `GetFriends`(iUserUnqeId int)
BEGIN

declare str1 int;
set str1=( select friendid from friend where userid=iUserUnqeId);


END$$

DELIMITER ;

when i call this iam getting this error i want all my friendid into str1

Error Code : 1242
Subquery returns more than 1 row
(0 ms taken)