MySQL permutation

Question

I have two tables. One has products and the other has bundles that go with it. I need to figure out the SQL that allows me to find all the combinations in which I can sell

Answer 1

Possible entirely within MySQL, though not simple. This example can handle up to 5 "extras", and is easily extensible for more:

CREATE TABLE products (name varchar(100), id int primary key);
INSERT INTO products (name, id) VALUES ('Bench', 1);

CREATE TABLE extra (name varchar(100), id int primary key, parent_id int references products.id, qty int);
INSERT INTO extra (name, id, parent_id, qty) VALUES 
  ('undershelf', 1, 1, 1), ('overshelf', 2, 1, 1), ('wheels', 3, 1, 1);

CREATE TABLE boolean_values (x boolean);
INSERT INTO boolean_values VALUES (TRUE), (FALSE);

CREATE VIEW product_extras_interim_vw AS
SELECT p.id product_id, p.name product_name, e.id extra_id, e.name extra_name, x
  FROM products p
  JOIN extra e ON (e.parent_id = p.id)
  CROSS JOIN boolean_values;

SELECT DISTINCT a.product_name
, CASE WHEN a.x THEN CONCAT(' + ', a.extra_name) END extra1
    , CASE WHEN b.x THEN CONCAT(' + ', b.extra_name) END extra2
    , CASE WHEN c.x THEN CONCAT(' + ', c.extra_name) END extra3
    , CASE WHEN d.x THEN CONCAT(' + ', d.extra_name) END extra4
    , CASE WHEN e.x THEN CONCAT(' + ', e.extra_name) END extra5
FROM product_extras_interim_vw a
LEFT JOIN product_extras_interim_vw b
  ON ( a.product_id = b.product_id
      AND b.extra_id > a.extra_id
  AND a.x )
LEFT JOIN product_extras_interim_vw c
  ON ( a.product_id = c.product_id
  AND c.extra_id > b.extra_id
      AND b.x )
LEFT JOIN product_extras_interim_vw d
  ON ( a.product_id = d.product_id
      AND d.extra_id > c.extra_id
      AND c.x)
LEFT JOIN product_extras_interim_vw e
  ON ( a.product_id = e.product_id
      AND e.extra_id > d.extra_id
      AND d.x)
ORDER BY product_name, extra1, extra2, extra3, extra4, extra5;

Output:

Bench
Bench + overshelf
Bench + overshelf + wheels
Bench + undershelf
Bench + undershelf + overshelf
Bench + undershelf + overshelf + wheels
Bench + undershelf + wheels
Bench + wheels