Question

I have a community driven database for an iOS game. I am trying to aggregate the data I’ve collected by the community, and it looks something like this:

+--------+--------+--------------+
| color1 | color2 | result_color |
+--------+--------+--------------+
| red    | blue   | purple       |
| blue   | red    | purple       |
| red    | blue   | purple       |
| yellow | blue   | green        |
+--------+--------+--------------+

Currently, I am running the following query:

select
    count(*) as count,
    `Mixes`.*
from
    `mixes` AS `Mixes`
where
    `result_color` = 'purple'
group_by
    color1,
    color2
order by
    `count` desc

Which produces the following output:

+-------+--------+--------+--------------+
| count | color1 | color2 | result_color |
+-------+--------+--------+--------------+
| 2     | red    | blue   | purple       |
| 1     | blue   | red    | purple       |
+-------+--------+--------+--------------+

However, I would like it to produce the following output, since when mixing colors it doesn’t matter which color you mix first:

+-------+--------+--------+--------------+
| count | color1 | color2 | result_color |
+-------+--------+--------+--------------+
| 3     | red    | blue   | purple       |
+-------+--------+--------+--------------+

So, my question is, how can I aggregate data over 2 columns such that when color1 is red and color2 is blue, that the aggregate function treats it the same as when color1 is blue and color2 is red?

Thanks in advance!

Answer 1

If you just have the two color columns you can simply order them with a CASE expression:

SELECT
  COUNT(*) AS `count`,
  CASE WHEN color1 < color2 THEN color1 ELSE color2 END AS color1,
  CASE WHEN color1 >= color2 THEN color1 ELSE color2 END AS color2,
  resultcolor
FROM mixes
WHERE resultcolor = 'purple'
GROUP BY
  CASE WHEN color1 < color2 THEN color1 ELSE color2 END,
  CASE WHEN color1 >= color2 THEN color2 ELSE color1 END,
  resultcolor
ORDER BY `count`;