Making a score table (hard) - mysql

Question

I need your help.
I have a database with a schema like this:
teams:
id
name
fundation_date
matchs:
id
date
id_local_team (foreign key to teams)
id_visit_team (foreign key to teams)
winner ('local', 'visit', 'draw')
players:
id
name
born
position ('arq','def','med','del')
id_team
goals:
id
id_match
id_player
time
and I need to do (among other things) this:
Show by team: Played matchs, winned matchs and drawn matchs (in different columns)
I have something like this:
SELECT t.name,
SUM(CASE t.id WHEN m.id_local_team THEN 1 WHEN m.id_visit_team THEN 1 ELSE 0 END) AS played,
SUM(CASE (CASE m.winner
WHEN 'local' THEN m.id_local_team
WHEN 'visit' THEN m.id_visit_team
ELSE NULL END)
WHEN t.id THEN 1
ELSE 0 END) AS winned,
SUM(CASE m.winner WHEN 'draw' THEN 1 ELSE 0 END) AS drawn
FROM teams AS t
INNER JOIN matchs AS m
ON (t.id = m.id_local_team OR t.id = m.id_visit_team)
GROUP BY t.name;
But that is giving me wrong results. Like, there are 8 matchs total, and the (4) teams are returning 12, 9, or 10 matchs winned (total of 43 matchs), a total of 16 winned matchs and a total of 10 drawn matchs. All above of 8.
What is happening??
In the full query I also have two more inner joins:
INNER JOIN players AS p
ON (p.id_team = t.id)
INNER JOIN goals AS g
ON (p.id = g.id_jugador)
I don't think it has nothing to do with these last ones. I know (think?) that i didn't do the matchs join correctly.
I appreciate if you have made it this far into the post!
The real schema is in spanish actually in Spanish (sorry for that guys) but here is all the magic:
SCHEMA
| equipos | CREATE TABLE `equipos` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`nombre` varchar(180) NOT NULL,
`f_fundacion` date DEFAULT NULL,
PRIMARY KEY (`id`)
)
| partidos | CREATE TABLE `partidos` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`fecha` datetime DEFAULT NULL,
`id_equipo_local` int(11) DEFAULT NULL,
`id_equipo_visitante` int(11) DEFAULT NULL,
`ganador` enum('local','visitante','empate') DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `fk_partidos_equipos_1` (`id_equipo_local`),
KEY `fk_partidos_equipos_2` (`id_equipo_visitante`),
CONSTRAINT `fk_partidos_equipos_1` FOREIGN KEY (`id_equipo_local`) REFERENCES `equipos` (`id`),
CONSTRAINT `fk_partidos_equipos_2` FOREIGN KEY (`id_equipo_visitante`) REFERENCES `equipos` (`id`)
)
QUERY
SELECT e.nombre,
SUM(CASE e.id WHEN p.id_equipo_visitante THEN 1 WHEN p.id_equipo_local THEN 1 ELSE 0 END) AS jugados,
SUM(CASE (CASE ganador
WHEN 'local' THEN p.id_equipo_local
WHEN 'visitante' THEN p.id_equipo_visitante
ELSE NULL END)
WHEN e.id THEN 1
ELSE 0 END) AS ganados,
SUM(CASE ganador WHEN 'empate' THEN 1 ELSE 0 END) AS empatados,
SUM(CASE (CASE ganador
WHEN 'local' THEN p.id_equipo_local
WHEN 'visitante' THEN p.id_equipo_visitante
ELSE NULL END)
WHEN e.id THEN 1
ELSE 0 END) * 3 + SUM(CASE ganador WHEN 'empate' THEN 1 ELSE 0 END) AS puntos,
COUNT(DISTINCT g.id) AS goles_a_favor
FROM equipos AS e
INNER JOIN partidos AS p
ON (e.id = p.id_equipo_visitante OR e.id = p.id_equipo_local)
INNER JOIN jugadores AS j
ON (j.id_equipo = e.id)
INNER JOIN goles AS g
ON (j.id = g.id_jugador)
GROUP BY e.nombre;
RESULTS
+----------------------------------+---------+---------+-----------+--------+---------------+
| nombre | jugados | ganados | empatados | puntos | goles_a_favor |
+----------------------------------+---------+---------+-----------+--------+---------------+
| Club Atlético All Boys | 12 | 6 | 3 | 21 | 3 |
| Club Atlético Chacarita Juniors | 12 | 3 | 0 | 9 | 3 |
| Club Atlético Ferrocarril Oeste | 9 | 3 | 3 | 12 | 3 |
| Club Atlético Tucumán | 10 | 4 | 4 | 16 | 2 |
+----------------------------------+---------+---------+-----------+--------+---------------+

Answer 1

You say that the full query contains joins to each goal made in a given match. This would lead to a situation where the each match is counted N times where N is the number of goals in the match. So for a 0-0 draw the match won't be counted at all, for a 1-0 match the match is counted once for the home team and zero times for the visiting team and 1-2 once for the home team and twice for the visiting team.
To check the number of goals in favor you should first calculate the the goal balance per match using a subquery or a view and then join with that. Then you won't have to problem caused by joining with the player-table.

Answer 2

It does look like the Matchs JOIN is a problem. So you are matching every match at least twice, once for the home team and once for the visiting team, but that doesn't quite explain 43 matches being displayed. Would it be possible to maybe see the full set of results? Sometimes SQL stuff can get touch to debug without access to the tables themselves, but at least seeing the results and what are duplicated might help.
You may want to join only on the winning teams - that should cut half of it out. Actually, since you seem to be trying to get match information, I would SELECT data FROM matches rather than teams. Selecting FROM the table that will limit your total selected rows is always your best bet, then JOIN from there.