wpdb get_row database query inquiry

Question

For Placehold to work, you should use $wpdb->query like:

$wpdb->query( 
  $wpdb->prepare( "
            SELECT * FROM mailer
            WHERE id = %d
        ",
        $_GET['caId']
    )
);

However in my opinion, the best option is to simply validate the get-parameter and than use it in $wpdb->get_results , like:

$catId = $_GET['caId'];
if(is_numeric($catId)){
   $_crds = $wpdb->get_results(" SELECT * FROM mailers WHERE id = $catId");

 foreach ($_crds as $_crds) {
   $_zipcodes = $_crds->zipcodes;
   $_maildate = $_crds->maildate;
 }
}