如何使用此代码显示所有条目并进行比较？

I have this code below that selects all id's for posts and then the snippet below that sees if there is a match. If a match it says duplicate. I tested it by using print command to print $test and print $unique but it only shows one id rather than all ids. How can i fix this code so it will display all id # and then compare to see if a duplicate exists and if exists it will say "duplicate."

         $sql="SELECT `Post_id` from `posts`";  
         $result=mysql_query($sql);

         $query = mysql_query($sql) or die ("Error: ".mysql_error());

         if ($result == "")
         {
         echo "";
         }
         echo "";


         $rows = mysql_num_rows($result);

         if($rows == 0)
         {
         print("");

         }
         elseif($rows > 0)
         {
         while($row = mysql_fetch_array($query))
         {

         $storedid = htmlspecialchars($row['Note_id']);

         print("");
         }

         }

       //This $test id exists and $storedid should contain 
       3VRDY but it still goes through

       $test = "3VRDY";

      if ( $storedid == $test ) {
  echo("duplicate");
      die();
      } else {
  echo("");

      }

Try this:

$test = '3VRDY';
while($row = mysql_fetch_array($query))
{
   $storedid = htmlspecialchars($row['Note_id']);
   if($storedid == $test)
        echo 'The ' . $storedid .' is duplicated<br/>';
   else
        echo 'The ' . $storedid .' is unique<br/>';
}

At the end of the loop you will have the results.