mysql replace text in a field php [duplicate] - php

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Closed 10 years ago.
Possible Duplicate:
mysql kill process is user dont got enought points PHP
i have a points system with user system where people can upgrade to [PRO] user with 50 points. When they register it automaticly write [user] down to my rights field. but now i want so after a'n action it check if they got 50 points and then replace [user] with [PRO] and then subtrac 50 points.
<?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========
$insert = "UPDATE `users` SET `points` = (`points`-50) WHERE `username` = '".$username."' and points > 50";
mysql_query($insert);
if (mysql_affected_rows() > 1)
{
// other codes
$insert = "UPDATE `users` SET `rights` = (`rights` [PRO]) WHERE `username` = '".$username."'";
mysql_query($insert);
header('location: succesupgrade.php');
}else{
echo "You don't have enough points to buy [PRO]";
}
?>
Again: i want so after people buy [PRO], the [user] get replaced with [PRO]. ANd then they lose 50 points. and if they dont got 50 points. echo says something.

Answer 1

Do it in one:
UPDATE `users`
SET `rights` = '[PRO]', points = points - 50
WHERE
`username` = 'somename'
AND points >= 50
AND rights != '[PRO]'
And just check whether you have an effected row or not. If they don't have enough points, it won't update, and neither will it when they already have the right. This avoids race conditions.