How to make such a selection on laravel (without using raw)?

Question

Laravel

Unsuccessful attempt

$query = DB::table('A')
            ->leftJoin('B', 'A.id', '=', 'B.A_id')
            ->whereNull('B.A');
        if ($id)
            $query->orWhere('A_id', $id);
        return $query->get();

Answer 1

What request is the Builder generating? You can see it like this ( from here ):

DB::connection()->enableQueryLog();
//To get an array of the executed queries, you may use the getQueryLog method:
dd(DB::getQueryLog());

Compare with what should be.
Personally, I sin on whereNull('B.A');instead of whereNull('B.A_id');.