多个 Union 和 Join 操作后的求和列

Question

我希望根据属于某个球队的球员对列的总数求和。我有一张球员桌和一张球队桌。目前，我没有问题，只是由于某种原因它不会总结我查询的最后一部分。这是我的代码示例：

Select SUM(points)
from (select points
from player
Join team on player.full_name=team.player1
Where team.team_id = 8
and week =9
UNION
Select points
FROM player 
JOIN team on player.full_name=team.player2 
Where team.team_id = 8
and week =9
UNION
Select points
FROM player 
JOIN team on player.full_name=team.player3
Where team.team_id = 8
and week =9
UNION
Select points
FROM player 
JOIN team on player.full_name=team.player4
Where team.team_id = 8
and week =9

任何关于为什么会发生这种情况的想法或完成它的更好的潜在方法将不胜感激！

Answer 1

您的查询似乎不完整，您必须使用 UNION ALL 来获得全部总数（如果 2 位或更多玩家拥有相同的点数，UNION DISTINCT 将消除这些行）：

SELECT
    SUM( points )
FROM (
    SELECT
        points
    FROM player
    JOIN team ON player.full_name = team.player1
    WHERE team.team_id = 8
    AND week = 9
    UNION ALL
    SELECT
        points
    FROM player
    JOIN team ON player.full_name = team.player2
    WHERE team.team_id = 8
    AND week = 9
    UNION ALL
    SELECT
        points
    FROM player
    JOIN team ON player.full_name = team.player3
    WHERE team.team_id = 8
    AND week = 9
    UNION ALL
    SELECT
        points
    FROM player
    JOIN team ON player.full_name = team.player4
    WHERE team.team_id = 8
) d

但我认为您的团队表需要更改以提高效率

请注意，使用 UNION = UNION DISTINCT 即如果省略，则假定为“不同”。

这可能更有效：

SELECT
    SUM( player.points )
FROM player
WHERE player.full_name IN (
    SELECT distinct
        case when cj.n = 1 then team.player1
             when cj.n = 2 then team.player2
             when cj.n = 3 then team.player3
             when cj.n = 4 then team.player4
        end
    FROM team
    cross join (
       select 1 as n union all
       select 2 as n union all
       select 3 as n union all
       select 4 as n
       ) cj
    WHERE team.team_id = 8
    )
AND player.week = 9    ;