soccerGameSeries

My solution:

CREATE PROCEDURE soccerGameSeries() 
BEGIN 
  SELECT IF(first_team_wins > second_team_wins, 1, 
                      IF(second_team_wins > first_team_wins, 2, IF( 
                      first_team_goals > second_team_goals, 1, IF( 
         second_team_goals > first_team_goals 
         , 2, IF( 
         first_team_away_goals > second_team_away_goals 
         , 1, IF( 
         second_team_away_goals > 
         first_team_away_goals, 2, 0)))))) AS winner 
  FROM   (SELECT SUM(IF(first_team_score > second_team_score, 1, 0)) AS 
                 first_team_wins, 
                 SUM(IF(second_team_score > first_team_score, 1, 0)) AS 
                 second_team_wins, 
                 SUM(first_team_score)                               AS 
                 first_team_goals, 
                 SUM(second_team_score)                              AS 
                 second_team_goals 
                        , 
                 SUM(IF(match_host = 1, first_team_score, 0))        AS 
                        first_team_home_goals, 
                 SUM(IF(match_host = 2, first_team_score, 0))        AS 
                        first_team_away_goals, 
                 SUM(IF(match_host = 1, second_team_score, 0))       AS 
                        second_team_away_goals, 
                 SUM(IF(match_host = 2, second_team_score, 0))       AS 
                        second_team_home_goals 
          FROM   scores) AS results; 
END