Mastering Eloquent Relationships

Laravel's Eloquent ORM provides a beautiful, simple ActiveRecord implementation for working with your database.

Defining Relationships

One-to-One

class User extends Model
{
    public function profile()
    {
        return $this->hasOne(Profile::class);
    }
}
class Profile extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

One-to-Many

class User extends Model
{
    public function posts()
    {
        return $this->hasMany(Post::class);
    }
}
class Post extends Model
{
    public function user()
    {
        return $this->belongsTo(User::class);
    }
}

Many-to-Many

class User extends Model
{
    public function roles()
    {
        return $this->belongsToMany(Role::class)
            ->withPivot('assigned_at')
            ->withTimestamps();
    }
}

Eager Loading

Prevent N+1 query problems with eager loading:

// Bad - N+1 queries
$users = User::all();
foreach ($users as $user) {
    echo $user->profile->bio; // Query for each user
}
// Good - Only 2 queries
$users = User::with('profile')->get();
foreach ($users as $user) {
    echo $user->profile->bio;
}
// Nested eager loading
$users = User::with(['posts.comments', 'profile'])->get();

Query Scopes

class Post extends Model
{
    public function scopePublished($query)
    {
        return $query->where('published_at', '<=', now());
    }
    public function scopeByAuthor($query, $userId)
    {
        return $query->where('user_id', $userId);
    }
}
// Usage
Post::published()->byAuthor(1)->get();