mysql cursor - select IDs in stament - mysql

Question

It returns IDs as string, it returns only one row which it has first ID. "7,6,5" It returns only 7; How can we correct this problem?
CREATE DEFINER=`root`#`localhost`
PROCEDURE `GET_COMPANION`(IN paramEmployeeId INT)
BEGIN
DECLARE counter INTEGER DEFAULT 0;
DECLARE v_finished INTEGER DEFAULT 0;
DECLARE v_companion varchar(100) DEFAULT "";
DECLARE v_companion_list varchar(100) DEFAULT "";
-- declare cursor for companion_id
DEClARE companion_cursor CURSOR FOR
SELECT companion_id FROM employee_has_companion ehc
WHERE ehc.employee_id = paramEmployeeId;
-- declare NOT FOUND handler
DECLARE CONTINUE HANDLER FOR NOT FOUND SET v_finished = 1;
OPEN companion_cursor;
get_companion: LOOP
FETCH companion_cursor INTO v_companion;
IF v_finished = 1 THEN
LEAVE get_companion;
END IF;
-- build companion list
SET v_companion_list = CONCAT(v_companion,",",v_companion_list);
END LOOP get_companion;
CLOSE companion_cursor;
SELECT * FROM companion co
LEFT JOIN citizenship ci
ON co.citizenship_id = ci.citizenship_id
WHERE co.companion_id IN( SUBSTRING(v_companion_list,
1,LENGTH(v_companion_list)-1));
END

Answer 1

You can use FIND_IN_SET(str,strlist) to check existence of a string in a list of comma separated values.
Change:
SELECT * FROM companion co
LEFT JOIN citizenship ci
ON co.citizenship_id = ci.citizenship_id
WHERE co.companion_id IN( SUBSTRING(v_companion_list,
1,LENGTH(v_companion_list)-1));
To:
SELECT * FROM companion co
LEFT JOIN citizenship ci
ON co.citizenship_id = ci.citizenship_id
WHERE FIND_IN_SET( co.companion_id, v_companion_list ) > 0;