Database One-to-Many with two foreign key fields in Laravel - database

Question

I have been trying to define some Database schema to use the laravel framework. I want to model a Football match. The first step I wanted to do is to define the Entity Relationship diagram, but I found this (which I thought would be quite trivial) to be confusing in some aspects.
First, the obvious approach is to say that a Match is related with two Teams, and a Team is related to any number of Matches. So, we would have a "Many to Many" relationship.
But the implementation of a many to many relation is to have two tables and an intermediate table to relate both entities. I think this would be too much, when I know that a Match will always have two Teams and simply having two columns (local_id and visitant_id) with foreign keys to the Teams table would be enough. Plus, I want to be able to do:
Match::find(1)->local() or Match::find(1)->visitant();
So, thinking on this I am implementing a "One to Many" relation, but with this I have another issue. To retrieve all the matches a Team has played I would like to do:
Team::find(1)->matches();
But I cannot do this because I can only specify one key column when defining the matches() method in eloquent (by default it would be team_id, but it should be visitant_id and local_id).

Answer 1

After some more digging into the source code I found there is a way to actually keep my database schema as it is and achieve what I want (at least in Laravel 4). I posted my problem in github and Taylor Otwell (creator of the framework) gave me the correct answer: https://github.com/laravel/framework/issues/1272
Quoting him, it should be as easy as this:
class Team extends Eloquent {
public function allMatches()
{
return $this->hasMany('Match', 'visitant_id')->orWhere('local_id', $this->id);
}
}
And then...
$team = Team::find(2);
$matches = $team->allMatches;

Answer 2

This is one of those famous database design problems. Friendship relationships, for instance, suffer from that same difficulty. Since you are using Eloquent, I would suggest you to stick with many to many approach and have an extra boolean column local on your intermediate table
class Match extends Eloquent {
public $includes = array('team'); // Always eager load teams
public function teams() {
return $this->has_many_and_belongs_to('team')->with('local');
}
public function get_local() {
foreach ($this->teams as $team) {
if ($team->pivot->local) return $team;
}
}
public function get_visitant() {
foreach ($this->teams as $team) {
if (!$team->pivot->local) return $team;
}
}
}
class Team extends Eloquent {
public function matches() {
return $this->has_many_and_belongs_to('match')->with('local');
}
// I'm doing separate queries here because a team may have
// hundreds of matches and it's not worth looping through
// all of them to retrieve the local ones
public function matches_as_local() {
return $this->has_many_and_belongs_to('match')->with('local')
->where('pivot_local', '=', 1);
}
public function matches_as_visitant() {
return $this->has_many_and_belongs_to('match')->with('local')
->where('pivot_local', '=', 0);
}
}
Obs:
The method has_many_and_belongs_to(...)->with('field') has nothing to do with eager loading. It tells Eloquent to load the intermediate table column field and put that in the pivot.
Usage:
$match = Match::find(1);
$match->local; // returns local team
$match->visitant; // returns visitant team
$team = Team::find(1);
$team->matches; // returns all matches
$team->matches_as_local; // ...
$team->matches_as_visitant; // ...
foreach ($team->matches as $match) {
if ($match->pivot->local) {
// put nice local icon here
} else {
// put nice visitant icon here
}
}