Question

我正在创建一个简单的数据库，这将允许我跟踪斯诺克结果，在玩家之间产生头对头的结果。目前我有3个表:(玩家，夹具，结果）

PlayerID    PlayerName
1           Michael Abraham
2           Ben Mullen
3           Mark Crozier

FixtureID   Date                 TableNo    Group
1           07/12/2015 19:00:00  12         0
2           08/12/2015 12:00:00  9          0

ResultID    FixtureID   PlayerID    FramesWon
1           1           1           3
2           1           3           1
3           2           1           5
4           2           2           1

我想要一个查询，它返回结果表中发生在1号和3号玩家之间的灯具的所有行。目前我的查询是：

SELECT *
FROM Result
WHERE PlayerID IN (1,3);

这将返回结果表的前3行 - 当我只查找前2行时，因为它们共享相同的FixtureID。是否有一种简单的方法可以从此查询结果中删除第三行，还是应该重新考虑我的数据库设计？任何帮助将不胜感激。

Answer 1

一种解决方案是使用GROUP BY查询，按FixtureID分组并计算每个FixtureID的行数。此查询将选择包含玩家1和3的所有FixtureID：

select
  FixtureID
from
  Results
where
  PlayerID IN (1,3)
group by
  FixtureID
having
  count(*)=2

然后从结果表中获取记录，您可以使用此查询：

select *
from Results
where FixtureID IN (
  select FixtureID
  from Results
  where PlayerID IN (1,3)
  group by FixtureID
  having count(*)=2
)

Answer 2

您可以加入您的灯具表两次，如下所示：

select
  *
from
  Result as R1
  join Result as R2 on R1.FixtureID = R2.FixtureID
where
  R1.PlayerID in (1,3)
  AND R2.PlayerID in (1,3)
  AND R1.PlayerID != R2.PlayerID
group by
  R1.FixtureID
;

或者，因为它现在有点乱，所以显示它像斯诺克分数显示经常显示：

select
  R1.FixtureID, R1.PlayerID as player1, R1.FramesWon as player1_frames, R1.FramesWon+R2.FramesWon as total_frames, R2.FramesWon as player2_frames, R2.PlayerID as player2
from
  Result as R1
  join Result as R2 on R1.FixtureID = R2.FixtureID
where
  R1.PlayerID in (1,3)
  AND R2.PlayerID in (1,3)
  AND R1.PlayerID != R2.PlayerID
group by
  R1.FixtureID
;

SQL Query返回列值多次出现的行

2 个答案: