最近在写一个发帖的接口，表那一块有点问题，下面是我的代码

下面是我写的，但是发现网站的版块主题列表页没有我这个接口的主题，请问少了些什么，而且这里会有一问题，经常出现错误，说是post表里发现重复值。

  //发表主题
   function Add_thread($fid,$uid,$author,$subject,$message){
    $timenow=time();
    DB::query("INSERT INTO ".DB::table('forum_thread')." (fid, posttableid, readperm, price, typeid, sortid, author, authorid, subject, dateline, lastpost, lastposter, displayorder, digest, special, attachment, moderated, status, isgroup, replycredit, closed)
        VALUES ('$fid', '0', '0', '0', '0', '0', '$author', '$uid', '$subject', '$timenow', '$timenow', '$author', '0', '0', '0', '0', '0', '244', '0', '0', '0')");
    $tid = DB::insert_id();
    if($tid>0)
    {
        $usesig=1;
        $first=1;
        $tid=Add_thread_post($fid,$tid,$first,$uid,$author,$subject,$timenow,$message,$usesig);
    }
    return $tid;
   }
   
  //发表帖子
  function Add_thread_post($fid,$tid,$first,$uid,$author,$subject,$timenow,$message,$usesig=0){
    $timenow=time();

    $first=($first==1)?1:0;
    $pid=DB::result_first("SELECT max(pid) FROM ".DB::table('forum_post'));
    $pid=$pid+1;

    DB::query("INSERT INTO ".DB::table('forum_post')." (pid,fid,tid,first,author,authorid,subject,dateline,message,useip,invisible,anonymous,usesig,htmlon,bbcodeoff,smileyoff,parseurloff,attachment,rate,ratetimes,status,tags,comment,replycredit)
        VALUES ('$pid','$fid','$tid','$first','$author','$uid', '$subject','$timenow','$message','10.0.0.150','0','0','$usesig','0','-1','-1','0','0','0','0','0','','0','0')");
    DB::query("update ".DB::table('forum_thread')." set replies=replies+1,lastpost=$uid,lastposter='$author' where tid=$tid");
    $pid = DB::insert_id();   
    return $pid;   
   }

另外还有一个问题，就是手机版的帖子里面的缩略图地址有在数据库里记录么。我要怎么找出这个缩略图地址。