confid je číslo konference
playerid je číslo řádku

změnil jsem kod na

<?php

 $confid = intval($_GET['conf']);
  $playerid = intval($_GET['playerid']);
$teams = $_POST['teams'];
$jmeno = $_POST['jmeno'];

 
if($_POST['update'])
{
mysql_query("UPDATE hraci SET teams = '$teams', jmeno = '$jmeno'WHERE confid=$confid AND playerid=$playerid ")or die(Mysql_error());
 
 
}
 
$sql = mysql_query("SELECT * FROM `hraci` WHERE confid=$confid AND playerid=$playerid limit 1 ")or die(mysql_error());
 
while($row = mysql_fetch_array($sql))
{
  
  echo "<form method='post'>";
  echo "<input type='text' name='nazev' value=".$row['teams'].">";
  echo "<input type='text' name='kod' value=".$row['jmeno'].">";
  echo "<input type='submit' name='update' value='Edituj' >";
  echo "</form>";
 
}
?>