How do I get all combinations of data from a MySQL

问题:

I have spent the last five hours trying to get every product option combination from a table but I'm totally stuck now. I have a table with data like (simplified):

CREATE TABLE `assigned_options` (
  `option_id` int(10) unsigned NOT NULL DEFAULT '0',
  `value_id` int(10) unsigned NOT NULL DEFAULT '0',
);

INSERT INTO `assigned_options` (`value_id`, `option_id`) VALUES
(4, 2),
(3, 2),
(2, 1),
(1, 1),
(5, 3),
(6, 3),
(7, 3);

Say option ID 2 is color with variations red (4) and blue (3), option id 1 size etc....

Is it possible to do this with one MySQL query? I have tried using PHP to make a recurring function to get every possibility but I just can't get it to work.

Any tips GREATLY appreciated. :)

回答1:

Given your table... I'm assuming you want every possible combo of value and option. That's a cross join (a join without any ON or where clause limiting the results):

 SELECT a.value_id, b.option_id 
     FROM assigned_options a 
     JOIN assigned_options b 
     GROUP BY a.value_id, b.option_id 

The group by filters out the duplicate results.

Do you have 2 other tables value and option that you want to pull all combinations of?

回答2:

select option_id, value_id
from assigned_options
group by option_id, value_id
order by option_id, value_id

回答3:

In TSQL you can use a recursive CTE, Can''t remember where I got it, but pretty sweet. Note MYSQL doesn't use "With" option, so it won't work in MySQL

WITH Numbers(N) AS (
                    SELECT N
                    FROM ( VALUES(1), (2), (3), (4), (5), (6)) Numbers(N)),
                        Recur(N,Combination) AS (
                        SELECT N, CAST(N AS VARCHAR(20)) 
                        FROM Numbers


UNION ALL

SELECT n.N,CAST(r.Combination + ',' + CAST(n.N AS VARCHAR(10)) AS VARCHAR(20)) 
FROM Recur r
INNER JOIN Numbers n ON n.N > r.N)



select Combination
from RECUR
ORDER BY LEN(Combination),Combination;