thinkphp如何实现分组获取满足条件的数据？

 thinkphp分组获取满足条件的数据：

<?php
//分组获取满足条件的一亩地ID
$cinema_id = $this->getCunIdById($change_num);

   //cun_use表(cun_id分组),获取要换取的大于该cun_use剩余的数量
    private function getCunIdById($change_num){
        $f="cu.cun_id,count(cu.id) as receive_num";
        $c=" and cu.cun_id != 0 and cu.cun_id= 2 and cu.user_id = 0 and cu.use_status = 0";
        $groupCunUse = $this->getExchageByCunId($c,$f);
        foreach ($groupCunUse as $gk => $gv) {
            if($gv['receive_num'] >= $change_num){
                $cinema_id =$gv['cinema_id'];
                break;
            }
        }
        return $cinema_id;
    }

  //cun_use表(cun_id分组),获取要换取的大于该cun_use剩余的数量
	public function getExchageByCunId($condition,$field){
		if (!$condition) {
			return false;
		}else{
			return M('cun_use')->table('cun_use cu,cun_piao cp')->where(' cu.cun_id = cp.cun_id'.$condition)->field($field)->group('tu.cun_id')->select();
		}
	}