如何解决解决mySQL中每个组的最大计分播放器
请参考另一个堆栈溢出问题here,但是那里的答案不包括group_id 3播放器。 我试图在MySQL中复制答案,但对PostgreSQL不熟悉。任何人都可以展示如何在MySQL中进行处理吗?
问题是要从每个组中将得分最高的球员作为winner_id
退回
create table players (
player_id integer not null unique,group_id integer not null
);
create table matches (
match_id integer not null unique,first_player integer not null,second_player integer not null,first_score integer not null,second_score integer not null
);
insert into players values(20,2);
insert into players values(30,1);
insert into players values(40,3);
insert into players values(45,1);
insert into players values(50,2);
insert into players values(65,1);
insert into matches values(1,30,45,10,12);
insert into matches values(2,20,50,5,5);
insert into matches values(13,65,10);
insert into matches values(5,3,15);
insert into matches values(42,8,4);
matches
表
match_id | first_player | second_player | first_score | second_score
----------+--------------+---------------+-------------+--------------
1 | 30 | 45 | 10 | 12
2 | 20 | 50 | 5 | 5
13 | 65 | 45 | 10 | 10
5 | 30 | 65 | 3 | 15
42 | 45 | 65 | 8 | 4
预期产量
group_id | winner_id
----------+-----------
1 | 45
2 | 20
3 | 40
解决方法
我认为,由于您无法使用另一个问题的解决方案,即您正在使用MySQL 5.7或更低版本。在这种情况下,您必须模拟ROW_NUMBER/PARTITION
功能,您可以使用从每个玩家本身的分数表中导出的LEFT JOIN
进行操作,并加入score
在第一个表中。任何在联合表中没有更高分数的玩家显然拥有最高分数。由于可以建立联系,因此我们从该表中选取最少的player_id
值(如果没有联系,则没有任何作用)。
SELECT group_id,MIN(player_id) AS player_id
FROM (
SELECT t1.group_id,t1.player_id
FROM (
SELECT p.player_id,p.group_id,SUM(CASE WHEN m.first_player = p.player_id THEN m.first_score
ELSE m.second_score
END) AS score
FROM players p
LEFT JOIN matches m ON m.first_player = p.player_id OR m.second_player = p.player_id
GROUP BY p.player_id,p.group_id
) t1
LEFT JOIN (
SELECT p.player_id,p.group_id
) t2 ON t2.group_id = t1.group_id AND t2.score > t1.score
GROUP BY t1.group_id,t1.player_id
HAVING COUNT(t2.player_id) = 0
) w
GROUP BY group_id
输出:
group_id player_id
1 45
2 20
3 40
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