รบกวนช่วยเช็คโค้ดนี้ให้หน่อยค่ะ เกี่ยวกับการ php และการ update ค่าใน ฐานข้อมูล

<?php
session_start();

// test
$_SESSION['username'] = "pat";


	$host = "localhost";
	$user = "root";
	$pass = "";
	$dbname = "kinderkids";
	$connection = mysql_connect($host, $user, $pass) or die ("cannot connect to DB");
	
		
	$sql = mysql_select_db($dbname,$connection) or die ("Couldn't find db");
	
	if (!$sql) {
	
	die ("cannot select database");
	
	} 
print_r($_SESSION);

$s_username = $_SESSION['username'];

//$score = ($_REQUEST['varScore']);
$score = 75;

if ($score) {

	$currentDate = date("Y-m-d");

	$tbsql = "SELECT username FROM testscore2 where username = '".$s_username."'";
	$result = mysql_query($tbsql)or die("error1");
	$num_rows = mysql_num_rows($result);

	if ($num_rows <> 0) {
		while ($row = mysql_fetch_assoc($result))
		{
			$dbcurrent =  $row['current_score'];
			//$dbprevious =  $row['previous_score'];
			echo $dbcurrent;
		
		}

		$updateQuery = "UPDATE testscore2 SET previous_score = '{$dbcurrent}' WHERE username = '".$s_username."'";
		//$updateQuery .= "WHERE username = '".$s_username."'";
		mysql_query($updateQuery) or die("error2");

		//$updatesql = "UPDATE testPreviousScore SET current_score = $score WHERE username = {$_SESSION['username']}";
		$updatesql = "UPDATE testscore2 SET current_score = '{$score}'";
		$updatesql .= "WHERE username = '".$s_username."'";
		mysql_query($updatesql) or die("error3");

	} else 


	$insertQuery = "INSERT INTO testscore2(username,last_visit, current_score) VALUES ('".$s_username."','$currentDate','$score')";

	mysql_query($insertQuery) or die("error4");



} else 

echo "no score posted";

?>