The crossJoinSub method of the query constructor

Using the CROSS JOIN subquery

use Illuminate\Support\Facades\DB;
 
$totalQuery = DB::table('orders')->selectRaw('SUM(price) as total');
 
DB::table('orders')
    ->select('*')
    ->crossJoinSub($totalQuery, 'overall')
    ->selectRaw('(price / overall.total) * 100 AS percent_of_total')
    ->get();

Tip given by @PascalBaljet