Firstly, I am sure this is a typo, but in your SQL example, 'notifications' is not a variable '$notifications'

Secondly, what you are doing here is re-assigning the variable '$notifications' . Depending on the results you are getting from your first query, you might want to try this:

$notifications = $notifications->where('volcano_id', '=', $id)->get();

This is then querying the results of your DB::select.

Notifications::where... Is basically query the DB again, so you are doubling up.

You are also checking $id twice. If your first query is right, then you won't need the second I don't think.

Hopefully that makes sense?