SQL MS Access连接帮助平均值不正确

Question

我正在尝试创建一个查询，以显示至少有一个团队参加比赛时的平均会议出席率。

人际关系

这非常接近我正在寻找的东西

SELECT 
    Conference.ConferenceName, 
    AVG(Game.Attendance) AS AVG_ATT
FROM 
    (
    Conference 
    INNER JOIN School ON Conference.[ConferenceID] = School.[ConferenceID]
    )
    INNER JOIN Game ON 
        (
        School.[SchoolID] = Game.[Team1] 
        OR 
        School.[SchoolID] = Game.[Team2]
        )
GROUP BY 
    Conference.ConferenceName;

问题是，如果一个游戏有2个来自同一会议的团队，则它将出席人数增加两次，并且应该只参加一次。

考虑2场比赛

游戏1

Team1- Wisconsin    
Conference - BIG10    
Team2 - Michigan    
Conference - BIG10
Attendance - 100,000

游戏2

Team1- Wisconsin    
Conference - BIG10
Team2 - USC
Conference - PAC12
Attendance - 65,000

结果

BIG10-correct    82,500  
PAC12            65,000     
BIG10-Actual     88,333

Answer 1

在派生的查询中按会议获取游戏的不同列表，然后进行平均。

SELECT
    ConferenceName,
    AVG(Attendance) AS AVG_ATT
FROM
    (
    SELECT DISTINCT
        GameID,
        Conference.ConferenceName, 
        Game.Attendance
    FROM 
        (
        Conference 
        INNER JOIN School ON Conference.[ConferenceID] = School.[ConferenceID]
        )
        INNER JOIN Game ON 
            (
            School.[SchoolID] = Game.[Team1] 
            OR 
            School.[SchoolID] = Game.[Team2]
            )
    ) DerivedDistinctGamesAndConferences
GROUP BY 
    ConferenceName;

Answer 2

使用UNION在进行平均之前先丢弃重复项

SELECT 
    Game.GameID        
    Game.Attendance
    Conference.ConferenceName
FROM 
    (
    Conference 
    INNER JOIN School ON Conference.[ConferenceID] = School.[ConferenceID]
    )
    INNER JOIN Game ON 
        (
        School.[SchoolID] = Game.[Team1]  -- TEAM 1
        )
UNION 
SELECT 
    Game.GameID        
    Game.Attendance
    Conference.ConferenceName
FROM 
    (
    Conference 
    INNER JOIN School ON Conference.[ConferenceID] = School.[ConferenceID]
    )
    INNER JOIN Game ON 
        (
        School.[SchoolID] = Game.[Team2]  -- TEAM 2
        ) 

这样您将获得query1 union query2

GameID   Attendance   Conference
  1         100,000      BIG10    <  one row will disapear
  2          80,000      BIG10
  1         100,000      BIG10    <  after union
  2          80,000      PAC12

然后，您可以计算该结果的平均值

Answer 3

我不确定在编码方面，但是从概念上讲，您需要汇总“至少有一个”团队时的总数这一事实（如您所说的，只有一次），这使我很了解您可能需要使用VBA脚本中的一些“ if ... then”子句语句可获取所需的特定计算。 目前，SQL的“或”语句还不够。