[jQuery] Multiple AJAX calls problem

[me-and-jQuery]

Hello. So I have a problem that when I get jQuery code in ajax
response and you click few times to activate ajax call, there are
multiple instances of same code. Lets see the example with keydown.

FILE 1:
<script>
$(document).ready(
        function() {
                        $("#my_div").click(function() {
                                        $.ajax({
                                                        type: "GET",
                                                        url: "test.php",
                                                        success: function(data) 
{
                                                                        
$("#div_ajax").html(data);
                                                        }
                                        })
                        })
        }
)
</script>
<div id="my_div">Click here</div>
<div id="div_ajax"></div>

FILE 2 - AJAX RESPONSE:
<script>
$().keydown(function(event) {
                alert(event.keyCode);
});
</script>
Ajax content loaded...

So, if I click on my_div twice, there will be two listeners for keys
and for same keydown two alerts.

I can solve this issue with ifs, but what is the best way to prevent
this behaviour? Maybe in the way of singletons or something?

Thanks for any advice, I am sure there must be simple and effective
solution. Have a nice day.