Querying Relations: Querying Relationship Absence

$posts = App\Post::doesntHave('comments')->get();

$posts = App\Post::whereDoesntHave('comments', function ($query) {
    $query->where('content', 'like', 'foo%');
})->get();

$posts = App\Post::whereDoesntHave('comments.author', function ($query) {
    $query->where('banned', 1);
})->get();