phpstock/app/admin/model/CgdCaixiao.php

<?php
declare (strict_types = 1);

namespace app\admin\model;

use think\Model;

/**
 * @mixin \think\Model
 */
class CgdCaixiao extends Model
{
    public function OriginCgd(){
    	return $this->belongsTo(OriginCgd::class,"cgdNo","newCode")->bind(["mainCode"=>"oldCode"]);
    }
}