TalkPHP - Small php error! - Thank you in advance!

how come i get,

Code:

Warning: mysql_fetch_row(): supplied argument is not a valid MySQL result resource in C:\wamp\www\code\watch.php on line 12

while($row = mysql_fetch_row($result)) // line 12.

Code:

and Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in C:\wamp\www\code\register.php on line 31

$num = mysql_num_rows($result); //line 31

right after i put in:

PHP Code:


		
			
$query = sprintf(" select * from users where username = '%s'",mysql_real_escape_string($username));

PHP Code:


		
			
$sql = sprintf("INSERT IGNORE INTO `upload` (`link`) VALUES ('%s')",mysql_real_escape_string($url));

Why ;S?

Thank you in advance!