用thinkphp查询数据库数据很慢，数据库有5万条数据，求大神帮忙优化

 if($_POST['shebei']!=""){
        $ysj=$dao->field('flags=0'.' and '."send_mac='".$_POST['shebei']."'")->select();
       
        $equ=$shebei->where("mac='".$_POST['shebei']."'")->limit(1)->find();
        $this->assign('equ',$equ);
       
        }
        $sjz=array();
        $sjss=array();
        $num=0;
        for($i=0;$i<count($ysj);$i++){
            $ysj[$i]['time']=strtotime($ysj[$i]['time']);
        }
        
        $ymd=$_POST['ktime'];
        $ymd1=$_POST['jtime'];
       
        $arrz=strtotime($ymd);//这里是第一个时间戳
        $arrz1=strtotime($ymd1);//这里是第二个时间戳 
        $ss=($arrz1-$arrz)/3600;
        $nums=array();
        for($k=0;$k<$ss;$k++){
            for($j=0;$j<count($ysj);$j++){
                    if($ysj[$j]['time']>($arrz+$k*3600)&&$ysj[$j]['time']<($arrz+($k+1)*3600)){
                     $sjz[$j]['mac']=$ysj[$j]['mac'];
                     $sjz[$j]['time']=date('Y-m-d H:i:s',$ysj[$j]['time']);
                     $sjz[$j]['sb']=$equ['address'];
                     $css[$j]['mac']=$ysj[$j]['mac'];
                     $sj=formatArray($css);                                                                                              }  
                                                }
                             }
                $i=0;
                $sjztime=array();
                $accs=array();
                $sb=array();                foreach($sjz as $v) {
                      if(! isset($sjztime[$v['mac']])){
                       $sjztime[$v['mac']] = $v;
                       $accs[$i]=$v;
                       $i++;
                                                      }
                                    }