Question

I have a users table with the following data:

+----+------------+--------------+--------------+--------------+
| id | name       | points_game1 | points_game2 | points_game3 |
+----+------------+--------------+--------------+--------------+
|  1 | player 1   |           10 |            0 |            5 |
|  2 | player 2   |            0 |           25 |            0 |
|  3 | player 3   |           30 |            3 |            0 |
|  4 | player 4   |            0 |            0 |           20 |
+----+------------+--------------+--------------+--------------+

I want to be able to show overall ranks, where the ranking is defined as the overall highest score rather than a ranking per game. So in the example above, what query would I use to display this result:

+----+------------+-------+----------------+
| id | name       | score | game           |
+----+------------+-------+----------------+
|  3 | player 3   |    30 | points_game1   |
|  2 | player 2   |    25 | points_game2   |
|  4 | player 4   |    20 | points_game3   |
|  1 | player 1   |    10 | points_game1   |
+----+------------+-------+----------------+

Answer 1

The following query answers your question:

SELECT 
  id, 
  name, 
  GREATEST(points_game1, points_game2, points_game3) AS score,
  CASE
    WHEN points_game1 = GREATEST(points_game1, points_game2, points_game3) THEN 'points_game1'
    WHEN points_game2 = GREATEST(points_game1, points_game2, points_game3) THEN 'points_game2'
    WHEN points_game3 = GREATEST(points_game1, points_game2, points_game3) THEN 'points_game3'
  END AS game
FROM
  users
ORDER BY 
  3 DESC

A bit crude due to repetitiveness of the GREATEST(…) calculation. You may wish to put that in a subquery.

At any case, make note that this query will not utilize any index on the table since the ORDER BY uses a function over columns — that negates usage of a key in MySQL.