tp6对于子查询

<?php
namespace app\index\controller;

use app\BaseController;
use think\facade\Db;
class Index extends BaseController
{
    public function hello()
    {
    	$res=Db::table('user')->field('id,title')->where('id','>',1)->fetchSql()->buildSql();//$res是子查询
    	$res1=Db::table($res.'  a')->where('a.title','like','cyg%')->order('id','desc')->fetchSql()->select();
//子查询怎么查呢？先内后外，也就是说先查询$res完毕在查询$res1。
//$res1是主查询
    
    	echo($res);
    	echo "<br />";
    	echo($res1);
    }
}