$results = DB::table('rooms')
->distinct()
->leftJoin('bookings', function($join)
{
$join->on('rooms.id', '=', 'bookings.room_type_id');
$join->on('arrival','>=',DB::raw("'2012-05-01'"));
$join->on('arrival','<=',DB::raw("'2012-05-10'"));
$join->on('departure','>=',DB::raw("'2012-05-01'"));
$join->on('departure','<=',DB::raw("'2012-05-10'"));
})
->where('bookings.room_type_id', '=', NULL)
->get();