OR operator slowing down MySQL query - mysql

Question

I have four tables each relating to the others by some fields: games, teams, altnames, countries.
Wrote this query with an OR operator in an ON clause (see line 6) which slows down the query very much:
select ROUND(AVG(attendance)), competition, team1, countries.* from games
LEFT JOIN (teams
INNER JOIN countries ON ( countries.iso3 = teams.country )
LEFT JOIN altnames ON ( altnames.entityType = "team" AND altnames.season = "1011" AND altnames.entityId = teams.longName )
)
ON ( altnames.altValue = games.team1 OR teams.longName = games.team1 )
where games.season="1011" group by games.competition, games.team1 having AVG(attendance)>= 500 order by AVG(attendance) desc
Query is fast enough when not using the OR, only one of the two conditions at a time:
1.
select ROUND(AVG(attendance)), competition, team1, countries.* from games
LEFT JOIN (teams
INNER JOIN countries ON ( countries.iso3 = teams.country )
LEFT JOIN altnames ON ( altnames.entityType = "team" AND altnames.season = "1011" AND altnames.entityId = teams.longName )
)
ON ( altnames.altValue = games.team1 )
where games.season="1011" group by games.competition, games.team1 having AVG(attendance)>= 500 order by AVG(attendance) desc
2.
select ROUND(AVG(attendance)), competition, team1, countries.* from games
LEFT JOIN (teams
INNER JOIN countries ON ( countries.iso3 = teams.country )
LEFT JOIN altnames ON ( altnames.entityType = "team" AND altnames.season = "1011" AND altnames.entityId = teams.longName )
)
ON ( teams.longName = games.team1 )
where games.season="1011" group by games.competition, games.team1 having AVG(attendance)>= 500 order by AVG(attendance) desc
Any idea why is this happening, and how the first query can be speed up?
EDIT:
Here are the tables:
altnames:
CREATE TABLE IF NOT EXISTS `altnames` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`entityType` enum('team','comp','logo') NOT NULL,
`entityId` varchar(50) NOT NULL DEFAULT '0',
`season` varchar(4) NOT NULL DEFAULT '0',
`altValue` varchar(50) NOT NULL DEFAULT '0',
KEY `id` (`id`),
KEY `entityType_season_altValue` (`entityType`,`season`,`altValue`)
)
countries:
CREATE TABLE IF NOT EXISTS `countries` (
`name` varchar(50) NOT NULL,
`iso2` varchar(2) NOT NULL,
`iso3` varchar(3) NOT NULL,
`color` varchar(7) NOT NULL,
KEY `iso3` (`iso3`)
)
games:
CREATE TABLE IF NOT EXISTS `games` (
`id` int(7) NOT NULL AUTO_INCREMENT,
`competition` varchar(10) NOT NULL,
`season` varchar(4) NOT NULL,
`stage` varchar(10) DEFAULT NULL,
`gamedate` date DEFAULT NULL,
`team1` varchar(50) NOT NULL,
`team2` varchar(50) NOT NULL,
`score1` tinyint(2) DEFAULT NULL,
`score2` tinyint(2) DEFAULT NULL,
`attendance` int(11) DEFAULT NULL,
`location` varchar(100) DEFAULT NULL,
`source` varchar(400) DEFAULT NULL,
`altsource` varchar(400) DEFAULT NULL,
`note` varchar(400) DEFAULT NULL,
KEY `id` (`id`),
KEY `competition_season` (`competition`,`season`),
KEY `team_comp_season` (`team1`,`competition`,`season`)
)
teams:
CREATE TABLE IF NOT EXISTS `teams` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`shortName` varchar(20) DEFAULT NULL,
`longName` varchar(50) NOT NULL,
`urlSlug` varchar(50) DEFAULT NULL,
`country` varchar(3) NOT NULL DEFAULT 'NSP',
`competitions` varchar(50) DEFAULT NULL,
`latitude` float(10,6) DEFAULT '0.000000',
`longitude` float(10,6) DEFAULT '0.000000',
`inactive` tinyint(1) DEFAULT '0',
KEY `id` (`id`),
KEY `long` (`longName`),
KEY `FK_teams_countries` (`country`),
CONSTRAINT `teams_ibfk_1` FOREIGN KEY (`country`) REFERENCES `countries` (`iso3`)
)

Answer 1

I just had a funny idea in mind While waiting for an expert opinion,
Try to switch OR operator with AND.
conditionA OR conditionB
is equivalent to
NOT(NOT(conditionA) and NOT(conditionB))
Good Luck,