laravel with relationship where code example

Example 1: laravel where on relation

Event::whereHas('participants', function ($query) {
    $query->where('IDUser', '=', 1);
})->get();

Example 2: laravel load relation on a relation

$books = Book::with('author.contacts')->get();

Example 3: eloquent relationships

$roles = App\User::find(1)->roles()->orderBy('name')->get();