The recordset is probably not returning a result. To test that, write the SQL to the page with:
<?php echo($query_rs_doppioni); ?>
Then test that in phpMyAdmin to see what it wrong and how it needs to be adjusted to return the result when you need it to. My guess is that your date field syntax needs to be updated, but I can't tell for sure without looking at the database and query like I'm advising you to.