nl-mall-api/app/Models/SkuModel.php

<?php

namespace App\Models;

use App\BaseApp\BaseModel;

class SkuModel extends BaseModel
{

    protected $table = 'sku';
    /**
     * The attributes that are mass assignable.
     *
     * @var list<string>
     */
    protected $guarded = [];

    public function product()
    {
        return $this->hasOne(ProductModel::class, 'id', 'product_id');
    }
}