When combining multiple queries into one how do you sum columns together

Question

I'm trying to calculate League Standings from a table of Matches.

+----------------------------------+
|              Matches             |
+----------------------------------+
| id                               |
| league_id (FK League)            |   
| season_id (FK Season)            |
| home_team_id (FK Team)           |
| away_team_id (FK Team)           | 
| home_score                       |
| away_score                       |
| confirmed                        |
+----------------------------------+

I can correctly calculate the Home League Standings using this query:

SELECT team.name, home_team_id AS team_id,
    COUNT(*) AS played,
    SUM((CASE WHEN home_score > away_score THEN 1 ELSE 0 END)) AS won,
    SUM((CASE WHEN away_score > home_score THEN 1 ELSE 0 END)) AS lost,
    SUM((CASE WHEN home_score = away_score THEN 1 ELSE 0 END)) AS drawn,
    SUM(home_score) AS goalsFor,
    SUM(away_score) AS goalsAgainst,
    SUM(home_score - away_score) AS goalDifference,
    SUM((CASE WHEN home_score > away_score THEN 3 WHEN home_score = away_score THEN 1 ELSE 0 END)) AS points
FROM matches
INNER JOIN team ON matches.home_team_id = team.id
WHERE league_id = 94
    AND season_id = 82
    AND confirmed IS NOT NULL
GROUP BY home_team_id
ORDER BY POINTS DESC;

And Away League Standigns using this query:

SELECT team.name, away_team_id AS team_id,
    COUNT(*) AS played,
    SUM((CASE WHEN away_score > home_score THEN 1 ELSE 0 END)) AS won,
    SUM((CASE WHEN home_score > away_score THEN 1 ELSE 0 END)) AS lost,
    SUM((CASE WHEN home_score = away_score THEN 1 ELSE 0 END)) as drawn,
    SUM(away_score) AS goalsFor,
    SUM(home_score) AS goalsAgainst,
    SUM(away_score - home_score) AS goalDifference,
    SUM((CASE WHEN away_score > home_score THEN 3 WHEN away_score = home_score THEN 1 ELSE 0 END)) AS points
FROM matches
INNER JOIN team ON matches.away_team_id = team.id
WHERE league_id = 94
    AND season_id = 82
    AND confirmed IS NOT NULL
GROUP BY away_team_id
ORDER BY points DESC;

But combining these two queries using UNION ALL I'm not getting correct result

SELECT * FROM 
(
    SELECT team.name, home_team_id AS team_id,
        COUNT(*) AS played,
        SUM((CASE WHEN home_score > away_score THEN 1 ELSE 0 END)) AS won,
        SUM((CASE WHEN away_score > home_score THEN 1 ELSE 0 END)) AS lost,
        SUM((CASE WHEN home_score = away_score THEN 1 ELSE 0 END)) AS drawn,
        SUM(home_score) AS goalsFor,
        SUM(away_score) AS goalsAgainst,
        SUM(home_score - away_score) AS goalDifference,
        SUM((CASE WHEN home_score > away_score THEN 3 WHEN home_score = away_score THEN 1 ELSE 0 END)) AS points
    FROM matches
    INNER JOIN team ON matches.home_team_id = team.id
    WHERE league_id = 94
        AND season_id = 82
        AND confirmed IS NOT NULL
    GROUP BY home_team_id
UNION
    SELECT team.name, away_team_id AS team_id,
        COUNT(*) AS played,
        SUM((CASE WHEN away_score > home_score THEN 1 ELSE 0 END)) AS won,
        SUM((CASE WHEN home_score > away_score THEN 1 ELSE 0 END)) AS lost,
        SUM((CASE WHEN home_score = away_score THEN 1 ELSE 0 END)) as drawn,
        SUM(away_score) AS goalsFor,
        SUM(home_score) AS goalsAgainst,
        SUM(away_score - home_score) AS goalDifference,
        SUM((CASE WHEN away_score > home_score THEN 3 WHEN away_score = home_score THEN 1 ELSE 0 END)) AS points
    FROM matches
    INNER JOIN team ON matches.away_team_id = team.id
    WHERE league_id = 94
        AND season_id = 82
        AND confirmed IS NOT NULL
    GROUP BY away_team_id
) x 
GROUP BY team_id
ORDER BY points DESC;

This should be the expected result:

Any idea on what I am doing wrong? Thanks!

Update 1:

Trying out Dans query doesn't work:

select team.name, HomePoints + AwayPoints points from team join ( select team.id, sum(case when home.home_score > home.away_score then 3 when home.home_score = home.away_score then 1 else 0 end) HomePoints, sum(case when away.away_score > away.home_score then 3 else 0 end) AwayPoints from team join matches home on team.id = home.home_team_id join matches away on team.id = away.away_team_id WHERE home.league_id = 94 AND home.season_id = 82 AND home.confirmed IS NOT NULL group by id ) temp on team.id = temp.id order by points desc;

I get this result:

Answer 1

You might wanna use a JOIN instead of a UNION. You are using a GROUP BY on the team_id after using the UNION on the subqueries that both have a team_id. That is not going to work... If you just use the join, you can even leave out the group by.