DB_app/app/Sold_products.php

<?php

namespace App;

use Illuminate\Database\Eloquent\Model;

class Sold_products extends Model
{
    public function empoyees_infs()
    {
        return $this->hasOne(Empoyees_inf::class, 'id', 'customer_id');
    }

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