SQL MS Access join help average not correct - sql

Question

I am trying to create a query that displays the average attendance by conference when at least one team was in a game.
Relationships
this is very close to what im looking for
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;
the problem is if a game has 2 teams from the same conference it adds the attendance twice, and should only do it once.
consider 2 games
game1
Team1- Wisconsin
Conference - BIG10
Team2 - Michigan
Conference - BIG10
Attendance - 100,000
game2
Team1- Wisconsin
Conference - BIG10
Team2 - USC
Conference - PAC12
Attendance - 65,000
Results
BIG10-correct 82,500
PAC12 65,000
BIG10-Actual 88,333

Answer 1

Get a distinct list of the games by conference in a derived query, then do your average.
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

USE UNION to discard duplicated first before doing the average
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
)
So you will get 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
Then you calculate the avergage over this result

Answer 3

I am not exactly sure in terms of coding, but conceptually, the fact that you need to aggregate totals "when at least one" team was- as you then say, only ONCE- at a conference, makes me intuit you may need to use some "if...then" clause statements within VBA script to get the specific calculation you want. Right now, the SQL "or" statement isn't enough.