JOIN serial data

CREATE TABLE categories(
 id int auto_increment primary key,
 title varchar(32)
);

CREATE TABLE products (
 id int auto_increment primary key,
 name varchar(32),
 cat_id varchar(32)
);

INSERT INTO categories (title)
VALUES
  ('Makanan'),
  ('Minuman'),
  ('Hangat'),
  ('Dingin');

INSERT INTO products (name, cat_id)
  VALUES
  ('Bakso', '1,3'),
  ('Es Juice', '2,4'),
  ('Pudding', '1,4'),
  ('Kopi', '2,3');

SELECT * FROM categories;
+----+---------+
| id | title   |
+----+---------+
|  1 | Makanan |
|  2 | Minuman |
|  3 | Hangat  |
|  4 | Dingin  |
+----+---------+
4 rows in set (0.00 sec)

SELECT * FROM products;

+----+----------+--------+
| id | name     | cat_id |
+----+----------+--------+
|  1 | Bakso    | 1,3    |
|  2 | Es Juice | 2,4    |
|  3 | Pudding  | 1,4    |
|  4 | Kopi     | 2,3    |
+----+----------+--------+
4 rows in set (0.00 sec)

SELECT p.id, p.name, GROUP_CONCAT(c.title ORDER BY c.id) as 'categories'
FROM products as p
LEFT JOIN categories AS c
    ON p.cat_id REGEXP CONCAT('[,]{0,1}', c.id, '[,]{0,1}')
GROUP BY p.id;

+----+----------+----------------+
| id | name     | categories     |
+----+----------+----------------+
|  1 | Bakso    | Makanan,Hangat |
|  2 | Es Juice | Minuman,Dingin |
|  3 | Pudding  | Makanan,Dingin |
|  4 | Kopi     | Minuman,Hangat |
+----+----------+----------------+
4 rows in set (0.00 sec)