How to remove duplicate values in a loop

[Anes]

Hi pals,
I plan to create a HTML rows using jQuery, where the
rows data come as JSON . When I take this data in a loop
the same data set is repeat twice , so get a duplicate
entry of already existing row.
my code is :

$("div#pre").html("");   
var j = 0;   
$.each(server_response.access_servers, function(i,access_servers){
  alert(access_servers.servername);
  var tblRow =
                        "<tr id=\"container_tr\">"
                        +"<td>"+access_servers.servername+"</td>"
                        +"</tr>"
                    $(tblRow).appendTo("div#pre");
  });

The JSON data has no duplicate value , So How can I eliminate this, reply me with ASAP.

Thankfully
Anes P.A