Ajax in WordPress to reload a SELECT every second

Solution:

this my.js in the js folder of the theme

jQuery(document).ready(function refresh_div() {
        jQuery.ajax({
           url:'//MySite/mysite/wp-admin/admin-ajax.php',
            action:'MyAjaxFunction',
            type:'POST',
            dataType:json,
            success:function(results) {
                jQuery(".result").html(results.result);
            }
        });
    }

    t = setInterval(refresh_div,1000););

the functions.php file of the theme adding this in the end:

function MyAjaxFunction(){
  //get the data from ajax() call
    $jsonresult = array();
    $TableContent = $wpdb->get_results("
            SELECT MAX(`post_date`) AS MaxDate FROM wp_posts"
    );
    foreach($TableContent as $Content){
    $jsonresult['result'] = $Content->MaxDate

    }
    echo json_encode($jsonresult);
        die();

  }
  // creating Ajax call for WordPress
   add_action( 'wp_ajax_nopriv_MyAjaxFunction', 'MyAjaxFunction' );
   add_action( 'wp_ajax_MyAjaxFunction', 'MyAjaxFunction' );