useraccount/app/model/AccountItem.php

<?php
declare (strict_types = 1);

namespace app\model;

use think\Model;

/**
 * @mixin \think\Model
 */
class AccountItem extends Model
{
      public function depart(){
    	return $this->belongsTo(CompanyItem::class,'itemid','id')->bind(['depart_name'=>'name']);
    }
}