mazanie riadkov

$sqlCheck = "SELECT * FROM $nazov_tabulky;";
$resultCheck = mysql_query($sqlCheck) OR die(mysql_error());
$numRowsCheck = mysql_num_rows($resultCheck);
if ($numRowsCheck >= 100)
  {
  // premaz tabulku
  $sqlPremaz = "TRUNCATE TABLE $nazov_tabulky;";
  $resultPremaz = mysql_query($sqlPremaz ) OR die(mysql_error());
  if ($resultPremaz) print "Premazal som 100 starych zaznamov.";
  }

// vloz zaznam
$sqlInsert = "INSERT INTO $nazov_tabulky('stlpec1','stlpec2', atd) VALUES('".$value1."','".$value2."', atd);";
$resultInsert = mysql_query($sqlInsert ) OR die(mysql_error());
if ($resultInsert) print "Zaznam vlozeny";
else print "Chyba. Zaznam neulozeny.";

<?php

class db_delete
{
   var $table_prefix;
   var $root_path = './';
   
   function $db_connect()
   {
      include_once ($this->root_path . 'config.php');
     mysql_connect($dbserver, $dbuser, $dbpassword) or die('Mysql error: Connecting db');
      mysql_select_db($dbname) or die('Mysql error: Selecting DB');
     $this->table_prefix = $table_prefix;
   }
   
   function db_num($db)
   {
      $this->db_connect();
      $sql = 'SELECT * FROM '.$db;
      $result = mysql_num_rows($sql);
      $num = mysql_num_rows($result);
      return $num;    
   }
   
   function delete($db)
   {
      $this->db_connect();
      $sql = 'DELETE FROM '.$db.' WHERE id < ('.$this->num($db).' - 30)';
     $result = mysql_query($sql);
   }
}

?>