MySQL: how to subtract an update - php

Question

i need to subtract an mysql update. here is the code:
<?php
session_start();
//=============Configuring Server and Database=======
$host = 'localhost';
$user = 'root';
$password = '';
//=============Data Base Information=================
$database = 'login';
$conn = mysql_connect($host,$user,$password) or die('Server Information is not Correct'); //Establish Connection with Server
mysql_select_db($database,$conn) or die('Database Information is not correct');
//===============End Server Configuration============
//=============Starting Registration Script==========
$username = mysql_real_escape_string($_POST['txtusername']);
//=============To Encrypt Password===================
//============New Variable of Password is Now with an Encrypted Value========
$insert = "UPDATE `users` SET `points` = (`points`-5) WHERE `username` = '".$username."'";
$insert = "UPDATE `users` SET `lodd` = (`lodd` +1) WHERE `username` = '".$username."'";
mysql_query($insert);
header('location: succes.php');
?>
the +1 work perfect but it dont work to -5... how can i do so that they get -5 points?

Answer 1

the +1 work correctly because the query with -5 will never be called as it is overwritten by the query that has +1.
you should have this code, (Although this is not the correct one)
$insert = "UPDATE `users` SET `points` = (`points`-5) WHERE `username` = '".$username."'";
mysql_query($insert);
// other codes
$insert = "UPDATE `users` SET `lodd` = (`lodd` +1) WHERE `username` = '".$username."'";
mysql_query($insert);
follow-up question: what are the dataypes of the two columns? are they unsigned or signed?

Answer 2

You're overwriting the first statement with the second. Try this:
$insert = "UPDATE `users` SET `points` = (`points`-5), `lodd` = (`lodd` +1) WHERE `username` = '".$username."'";
mysql_query($insert);