Well, you could use something like this.
You will have to SELECT * FROM table WHERE something="$something"
$sql = mysql_query("SELECT * FROM table);
$login_check = mysql_num_rows($sql);
if($login_check > 0)
{
echo"Darn! You found my row!";
}
else
{
echo"Whoopie, my row is still hidden.";
}
You can modify the script for your own needs.
-Blake