overenie

//overenie jedinecnosti
      $query2 = "
      SELECT *
      FROM tabulkaClenov
      WHERE nick='$nick'
      ";
        $result2 = mysql_query($query2);
        $pocetRiadkov = mysql_num_rows($result2);
        if($pocetRiadkov == 1) { $chyby.="Toto prihlasovacie meno už je použité.<br>"; }
      $query2 = "
      SELECT *
      FROM tabulkaClenov
      WHERE mail='$mail'
      ";
        $result2 = mysql_query($query2);
        $pocetRiadkov = mysql_num_rows($result2);
        if($pocetRiadkov == 1) { $chyby.="Tento e-mail už je použitý.<br>"; }
           

if($chyby!="") { echo $chyby; }

//connect, select_db a podobné kraviny
$query = "SELECT 0 FROM uzivatelia WHERE nick='{$premenna}'"
$result = mysql_query($query);
$is_nick_used = (mysql_num_rows($result)) ? true:false;

include "config.php";
$query = "SELECT * FROM users WHERE login=\"".$_POST['login']."\"";
$result = mysql_query($query, $link) or die ("Chyba!");
$num = mysql_num_rows($result);
if ($num != 0){
echo "Niekto už používa rovnaký login!";
die();
}