Laravel Eloquent: Subqueries for Complex Queries

$users = User::addSelect(['latest_post' => Post::select('title')
    ->whereColumn('user_id', 'users.id')
    ->latest()
    ->take(1)
])->get();

$users = User::orderByDesc(
    Post::select('created_at')
        ->whereColumn('user_id', 'users.id')
        ->latest()
        ->take(1)
)->get();

$users = User::whereIn('id', function ($query) {
    $query->select('user_id')
        ->from('posts')
        ->where('is_published', true);
})->get();