Функцией вывести несколько строк одного столбца

DROP FUNCTION IF EXISTS sp_get_manuf_less_avg;
 
DELIMITER $$
 
CREATE FUNCTION sp_get_manuf_less_avg ()
RETURNS VARCHAR(50)
DETERMINISTIC
BEGIN
    DECLARE title VARCHAR(50) DEFAULT "none";
 
    SELECT name INTO title
    FROM manufacturers m JOIN(
        SELECT id_manufact, SUM(price)
        FROM products
        GROUP BY id_manufact
        HAVING SUM(price) < ALL(
            SELECT SUM(p.price) / COUNT(DISTINCT m.name)
            FROM products p
            JOIN manufacturers m
            ON p.id_manufact = m.id_manufact)) t
    ON m.id_manufact = t.id_manufact
    LIMIT 1;
        
    RETURN title;
END $$
 
DELIMITER ;
 
SELECT sp_get_manuf_less_avg ();

CREATE TABLE IF NOT EXISTS manufacturers(
  id_manufact INTEGER PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(30) NOT NULL,
  sum_prod DECIMAL (10, 2) NOT NULL
) ENGINE InnoDB DEFAULT CHARSET = UTF8;
 
CREATE TABLE IF NOT EXISTS products (
  id_prod INTEGER PRIMARY KEY AUTO_INCREMENT,
  name VARCHAR(50) NOT NULL,
  id_manufact INTEGER NOT NULL,
  price DECIMAL (10, 2) NOT NULL,
  in_stock INTEGER NOT NULL,
  FOREIGN KEY (id_manufact) REFERENCES manufacturers(id_manufact)
) ENGINE InnoDB DEFAULT CHARSET = UTF8;