Question

我有一个比赛的比赛表。

这里是mysql表：

<头>

id	玩家1	player1_score	player1_rating	玩家2	player2_score	player2_rating	tourney_id	回合
1	1	9	1.05	2	3	5.34	5	1
2	3	4	5.21	4	9	3.34	5	1
3	5	9	3.52	6	2	5.24	5	1
4	1	9	6.23	3	0	4.74	5	2
5	2	8	9.43	4	9	1.23	5	2
6	3	9	3.41	5	7	6.23	5	2
7	1	9	5.22	4	2	2.43	5	3
8	2	3	4.21	3	9	5.22	5	3
9	5	1	7.31	6	9	3.43	5	3

如何获得特定锦标赛中每位球员的平均球员评分？请注意，有两列包含玩家 ID (player1, player2)

Answer 1

根据您的要求（即使您没有给我们您的预期结果），我认为您的代码应该是这样的：

 SELECT (SELECT SUM(player1_rating) / COUNT(DISTINCT player1)
            FROM your_table GROUP BY player1) as avg_player1, 
           (SELECT SUM(player2_rating) / COUNT(DISTINCT player2) FROM your_table 
           GROUP BY player2) as avg_player2
    FROM your_table

Answer 2

我将查询修改为：

SELECT player_id
    , tourney_id
    , avg_player_rating = SUM(player_rating) / SUM(cnt)
FROM (

    SELECT player_id = player1
        , tourney_id
        , player_rating = SUM(player1_rating)
        , cnt = COUNT(*)
    FROM tournament
    GROUP BY tourney_id, player1

    UNION ALL

    SELECT player_id = player2
        , tourney_id
        , player_rating = SUM(player2_rating)
        , cnt = COUNT(*)
    FROM tournament
    GROUP BY tourney_id, player2

) AS a
GROUP BY player_id, tourney_id

这将给出结果：

player_id   tourney_id   avg_player_rating
----------  ----------   --------------------
 1           5            4.1666
 2           5            6.3266
 3           5            4.6450
 4           5            2.3333
 5           5            5.6866
 6           5            4.3350

我希望这是您正在寻找的结果。

如何选择具有相同外键的两个列的平均值

2 个答案: