mysql - 来自不同列的分组值和计数

Question

我有这张表:

UNIQUE_ID | WINNER_ID | FINALIST_ID
________1 | ________1 | __________2
________2 | ________1 | __________3
________3 | ________3 | __________1
________4 | ________1 | __________2

我需要一份所有玩家(获胜者和决赛入围者)的列表以及他们获得第一名或第二名的次数。

在这种情况下，它将是:

PLAYER_ID | WINNER_TIMES | FINALIST_TIMES
________1 | ___________3 | _____________1
________2 | ___________0 | _____________2
________3 | ___________1 | _____________1

这里已经问过类似的问题 ( LINK )，但我不明白答案。

Answer 1

select  coalesce(winner_id, finalist_id) as PLAYER_ID
,       count(winner_id) as WINNER_TIMES
,       count(finalist_id) as FINALIST_TIMES
from    (
        select  winner_id
        ,       null as finalist_id
        from    YourTable
        union all
        select  null
        ,       finalist_id
        from    YourTable
        ) as SubQueryAlias
group by
        coalesce(winner_id, finalist_id)

Live example at SQL Fiddle.