MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

CREATE TABLE table_a
    (`cod_item` varchar(5), `Order` int)
;
    
INSERT INTO table_a
    (`cod_item`, `Order`)
VALUES
    ('1,2,3', 1),
    ('2,4,5', 2),
    ('2', 3),
    ('5,6,7', 1)
;
CREATE TABLE table_b
    (`cod_item` int, `Name` varchar(10))
;
    
INSERT INTO table_b
    (`cod_item`, `Name`)
VALUES
    (1, 'prod_1'),
    (2, 'prod_2'),
    (3, 'prod_3'),
    (4, 'prod_4')
;
SELECT `Order`,GROUP_CONCAT(CONCAT(b.`cod_item` ,' - ', b.`Name`) ORDER BY b.`cod_item`)
FROM table_a a LEFT JOIN table_b b ON  FIND_IN_SET(b.`cod_item`,a.`cod_item`)
GROUP BY `Order`


Order
GROUP_CONCAT(CONCAT(b.`cod_item` ,' - ', b.`Name`) ORDER BY b.`cod_item`)


1
1 - prod_1,2 - prod_2,3 - prod_3

2
2 - prod_2,4 - prod_4

3
2 - prod_2

Order	GROUP_CONCAT(CONCAT(b.`cod_item` ,' - ', b.`Name`) ORDER BY b.`cod_item`)
1	1 - prod_1,2 - prod_2,3 - prod_3
2	2 - prod_2,4 - prod_4
3	2 - prod_2