sorting by relation

[ahmetsabri]

public function fields(): PowerGridFields
{
    return PowerGrid::fields()
        ->add('reference_number')
        ->add('customer_name', function (Order $order) {
            return $order->customer->full_name;
        })
        ->add('package', function (Order $order) {

            $string = '<div data-bs-toggle="tooltip" data-bs-custom-class="tooltip-info" title="' . $order->getItemServiceNames() . '"><strong class="">' . $order->service->title . '</strong><br>';
            if ($order->orderItems?->count()) {
                $string .= '<small>+ ' . $order->extraOrderItems?->count() . ' services</small></div>';
            }
            return $string;

        })
        ->add('total_amount', function (Order $order) {
            return money($order->totalGrossPrice, $order->currency, true);
        })
        ->add('status', function (Order $order) {

            return '<span class="badge bg-' . $order->getStatusColor() . '">' . $order->getStatus() . '</span>';

        })->add('created_at')
        ->add('discount_val', function ($order) {

            if ($order->coupon) {
                return money((int) $order->discount, $order->currency);
            } else {
                return 'N/A';
            }

        })
        ->add('discounted_amount', function ($order) {

            if ($order->calculateFinalPrice()) {
                return '<span class="fw-bold">' . money($order->calculateFinalPrice(), $order->currency) . '</span>';
            }
            return 'N/A';


        })->add('actionss', function ($order) {

            return Blade::render('central::orders.columns.table-actions', ['order' => $order]);


        });

}

public function columns(): array
{
    return [
        Column::make('reference number', 'reference_number')
            ->searchable()
            ->sortable(),

        Column::make('Customer Name', 'customer_name')
            ->sortable(),

        Column::make('Package', 'package')
            ->searchable(),

            Column::make('Total Amount', 'total_amount')->sortable(),
            Column::make('Discount', 'discount_val'),
            Column::make('Status', 'status'),
        Column::make('Discounted Amount', 'discounted_amount'),

        Column::make('actionss', 'actionss')
    ];
}

how can sort by `customer_name` 

[Honokai]

Have you tried following this link?
Sorting

If your problem still persist, I will need more details on your current structure, some items like your model, relations and anything that would help on assisting you.