How to get information in jquery function from the php file

Hello guys my question is how to get an db information (in my case points just a number) from the php file to the jquery ajax script so here is my jquery:

function rate_down(id) { 
    var id = id;
//submit data to php script

    var data = {
      "id": id,
    };

    $.ajax({
      type: "POST",
      url: "rating.php",
      data: data,
      success: function(response) {

      var currentValue = /* here i want to put the db number */
      var newValue = +currentValue - 1;
      $("#points_"+id).text(newValue);




      },
      error: function(jqXHR, textStatus, errorThrown){
        alert(errorThrown);
      } 
    });
};

And i want my raiting.php im not sure if i shoud post it becouse its usless but here is my mysql query in raiting.php:

$pic_id = (int) $_REQUEST['id'];
mysql_query = mysql_query"SELECT points FROM `photos` WHERE `id` = '$pic_id'";