MySQL查詢排名

Question

我有以下數據的用戶表：

 
+----+------------+--------------+--------------+--------------+ 
| 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 | 
+----+------------+--------------+--------------+--------------+ 

我希望能夠表現出整體的行列，其中排名被定義爲總體最高得分，而不是排名每場比賽。所以在上面的例子中，我會用什麼查詢，顯示結果如下：

 
+----+------------+-------+----------------+ 
| 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

下面的查詢回答你的問題：

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 

有點粗，由於最大的重複性（... ）計算。你可能希望把它放在子查詢中。

在任何情況下，請注意，由於ORDER BY在列上使用了一個函數，因此該查詢不會使用表上的任何索引 - 這會否定MySQL中的密鑰使用。