ajax一次显示mysql内容

my page should update with mysql table content always. i made a ajax function. but when i click refresh button, duplicating same result. i want to show one table raw only once. here is my ajax function.

//page upload function

                 $("#display").click(function() {                

                    $.ajax({    //create an ajax request to load_page.php
                        type: "POST",
                        url: "display_status.php",             
                        dataType: "text",   //expect html to bereturned                
                        success: function(response){                    
                            $("#responds").append(response);
                            //alert(response);
                        }

                    });
                });

        });
        </script>


     <ul id="responds">

    </ul> 
      <input type="button" id="display" value="Refresh Page" />

then this is my php page (display_status.php)

    $results = $dbc->query("SELECT * FROM status where student_id='$stu_id'");
    //get all records from add_delete_record table
    while($row = $results->fetch_assoc())
    {
      echo '<li id="item_'.$row["status_id"].'">';
      echo '<div class="del_wrapper"><a href="#" class="del_button" id="del-'.$row["status_id"].'">';
      echo '<img src="images/icon_del.gif" border="0" />';
      echo '</a></div>';
      echo $row["status"].'</li>';

instead of append ,use this:

var prev=$("#responds").text();
var res=prev+response;
$("#responds").html(res);