getJSON + json_encode + query php

This is my query.php

<?php
 $db_host="localhost";
 $db_user="root";
 $db_pass="root";
 $db_name="mytable"; 
 
 mysql_connect("$db_host","$db_user","$db_pass")or die(""); 
 mysql_select_db("$db_name")or die("");
 
 $query = "SELECT * FROM app"; 
 $result=mysql_query($query);  
 echo json_encode(mysql_fetch_assoc($result)); 
 ?>
 

How can i do to learn any single attribute in my html page?
I try like this but it dont work.

$.getJSON("query.php",function(result){
    $.each(result, function(i, obj){
      $('div').html(obj.attribute1+" "+obj.attribute2 ecc...);
    });
  });
 

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