Basit bir sıralamada sorun yardım!

<?php
 $con=mysqli_connect("localhost","....","....","....");
 // Check connection
 if (mysqli_connect_errno())
   {
   echo "Failed to connect to MySQL: " . mysqli_connect_error();
   }
mysqli_query($con,"SET @r=0;");
mysqli_query($con,"UPDATE players SET Ranking= @r:= (@r+1) ORDER BY puan DESC");
mysqli_close($con);
 ?>