Gong-Ying-Lian-API/app/common/model/CustomerSpecBack.php

<?php
declare(strict_types=1);

namespace app\common\model;

use think\Model;

class CustomerSpecBack Extends Model
{

      //customer_spec spec_back
      //customer
      public function customer()
      {
            return $this->hasOne(Customer::class,'id','customer_id');
      }
}