phpstock/app/admin/model/ThStock.php

<?php
declare (strict_types = 1);

namespace app\admin\model;

use think\Model;

/**
 * @mixin \think\Model
 */
class ThStock extends Model
{
 
	public function purcheaseOrder(){
		return $this->belongsTo(PurcheaseOrder::class,"rela_cgdNo","cgdNo");
	}
}