Question

for a soccer league i have two tables:

• “teams” is a table that lists all teams as unique entries (‘id’,
  ‘team_name’)
• “matches” is a table that shows the match results: In the columns
  ‘home’ and ‘away’ i save each game result. ‘home_team_id’ and
  ‘away_team_id’ is the association to the teams-table.

This is how my query looks like:

SELECT Teams, Sum(P) as 'Matches', Sum(W) as 'win', Sum(D) as 'draw', Sum(L) as 'lost',
       SUM(Pts) as 'points'
  FROM (
        SELECT home Teams, 1 P,
                IF (home > away,1,0) W,
                IF (home = away,1,0) D,
                IF (home < away,1,0) L,
                CASE 
                    WHEN home > away THEN 3
                    WHEN home = away THEN 1 
                    ELSE 0
                END PTS
          FROM `matches`

        UNION ALL
        SELECT away Teams, 1,
                IF (home < away,1,0),
                IF (home = away,1,0),
                IF (home > away,1,0),
                CASE 
                    WHEN home < away THEN 3
                    WHEN home = away THEN 1
                    ELSE 0
                END
          FROM `matches`
        ) AS ERG
GROUP BY Teams
ORDER BY SUM(Pts) DESC 

Now i want the team names (teams.team_name) from the team-table. To achieve this i tried several join-statements with no luck.

It’s obvious that the teams-table can contain teams who did not attend a match. These teams need to be displayed with zero-results.

Therefore I tried a LEFT JOIN:

SELECT team_name AS 'Teams'
  FROM `teams`
  LEFT JOIN matches ON ( teams.id = matches.home_team_id )

right after the ORDER-line in the end. I got an error message.
I use MySQL 5.1.44, so nested selects shouldn’t be a problem.

Any idea?

Answer 1

It sounds like you want to do something like this. I updated your sub-queries to include the home_team_id and the away_team_id, then you will JOIN on the teams table to return the name.:

SELECT Teams, 
  Sum(P) as 'Matches',
  Sum(W) as 'win',
  Sum(D) as 'draw',
  Sum(L) as 'lost',
  SUM(Pts) as 'points',
  h.team_name as HomeTeam,
  a.team_name as AwayTeam
FROM
(
  SELECT home Teams,
    1 P,
    IF (home > away,1,0) W,
    IF (home = away,1,0) D,
    IF (home < away,1,0) L,
    CASE WHEN home > away THEN 3 WHEN home = away THEN 1 ELSE 0 END PTS,
    home_team_id,
    away_team_id
  FROM `matches`

  UNION ALL

  SELECT away Teams,
    1,
    IF (home < away,1,0),
    IF (home = away,1,0),
    IF (home > away,1,0),
    CASE WHEN home < away THEN 3 WHEN home = away THEN 1 ELSE 0 END,
    home_team_id,
    away_team_id
  FROM `matches`
) AS ERG
LEFT JOIN `teams` h
  on ERG.home_team_id = h.home_team_id
LEFT JOIN `teams` a
  on ERG.away_team_id = a.away_team_id
GROUP BY Teams, home_team_id, away_team_id
ORDER BY SUM(Pts) DESC 

Edit #1 based on your comments, it sounds like you want this (See SQL Fiddle with Demo):

SELECT TeamId, 
  t.team_name,
  Teams, 
  Sum(P) as 'Matches', 
  Sum(W) as 'win', 
  Sum(D) as 'draw', 
  Sum(L) as 'lost',
  SUM(Pts) as 'points'
FROM 
(
  SELECT home_team_id TeamId, 
      home Teams, 1 P,
      IF (home > away,1,0) W,
      IF (home = away,1,0) D,
      IF (home < away,1,0) L,
      CASE 
          WHEN home > away THEN 3
          WHEN home = away THEN 1 
          ELSE 0
      END PTS
  FROM `matches`

  UNION ALL
  SELECT away_team_id TeamId,
       away Teams, 1,
       IF (home < away,1,0),
       IF (home = away,1,0),
       IF (home > away,1,0),
       CASE 
           WHEN home < away THEN 3
           WHEN home = away THEN 1
           ELSE 0
        END
   FROM `matches`
) AS ERG
LEFT JOIN `teams` t
  ON ERG.TeamId = t.id
GROUP BY Teams, TeamId
ORDER BY SUM(Pts) DESC