อยากทราบว่าผมเขียนเงือนไขแล้วในการ insert ข้อมูลแล้วแต่พอเวลามีข้อมูลซ้ำให้เปลี่ยนเป็น update แทนแต่ไม่เปนไปตามเงือนไขครับ

<?php require_once('Connections/nongchumsaengwittaya.php'); ?>
<?php
if (!function_exists("GetSQLValueString")) {
function GetSQLValueString($theValue, $theType, $theDefinedValue = "", $theNotDefinedValue = "") 
{
  $theValue = get_magic_quotes_gpc() ? stripslashes($theValue) : $theValue;

  $theValue = function_exists("mysql_real_escape_string") ? mysql_real_escape_string($theValue) : mysql_escape_string($theValue);

  switch ($theType) {
    case "text":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;    
    case "long":
    case "int":
      $theValue = ($theValue != "") ? intval($theValue) : "NULL";
      break;
    case "double":
      $theValue = ($theValue != "") ? "'" . doubleval($theValue) . "'" : "NULL";
      break;
    case "date":
      $theValue = ($theValue != "") ? "'" . $theValue . "'" : "NULL";
      break;
    case "defined":
      $theValue = ($theValue != "") ? $theDefinedValue : $theNotDefinedValue;
      break;
  }
  return $theValue;
}
}

mysql_select_db($database_nongchumsaengwittaya, $nongchumsaengwittaya);
$query_chk_data = "SELECT * FROM tbstudent where Student_Id='$data1'";
$chk_data = mysql_query($query_chk_data, $nongchumsaengwittaya) or die(mysql_error());
$row_chk_data = mysql_fetch_assoc($chk_data);
$totalRows_chk_data = mysql_num_rows($chk_data);
    if ( $_FILES['file']['error'] ) { 
        die("upload error "); 
    } 
  
 //======Connect DB======================//   
    $m_host = "localhost"; 
    $m_user = "root"; 
    $m_pass = "1234"; 
    $m_name = "nongchumsaengwittaya"; 

    mysql_connect($m_host,$m_user,$m_pass);  
    mysql_select_db($m_name); 
    mysql_query("SET NAMES UTF8"); 
 //======End Connect DB======================//   

 //======Get data from Excel======================//        
    $dom    =    DOMDocument::load( $_FILES['file']['tmp_name'] ); 
    $rows    =    $dom->getElementsByTagName( 'Row' ); 
    $row    =    1; 
     
    foreach ($rows as $temp) { 
        $col = 1; 
        if($row==1) { 
            $row++; continue; 
        } 
        $cells    = $temp->getElementsByTagName('Cell'); 
		
        foreach( $cells as $cell )  { 
             if($col==1) $data1 = $cell->nodeValue; 
             if($col==2) $data2 = $cell->nodeValue; 
             if($col==3) $data3 = $cell->nodeValue;
             if($col==4) $data4 = $cell->nodeValue; 
             $col++; 
        } 
 //======End Get data from Excel======================//        

//==================Insert To DB ====================================//
if($row_chk_data){
	$sql = " INSERT INTO tbstudent (";		
	$sql .= " Student_Id, ";		
	$sql .= " Student_Name, ";		
	$sql .= " Student_Surname, ";		
	$sql .= " Student_Room ";		
	$sql .= " ) VALUES ( ";		
	$sql .= " '$data1', ";		
	$sql .= " '$data2', ";		
	$sql .= " '$data3', ";	
	$sql .= " '$data4' ";		
	$sql .= " ) ";		
	mysql_query($sql) or die(mysql_error()); 
	}else{
	$sql = " update tbstudent set Student_Id='$data1',Student_Name='$data2',Student_Surname='$data3',Student_Room='$data4' where Student_Id='$data1'";			
	mysql_query($sql) or die(mysql_error()); 
//==================End Insert To DB ====================================//
 $row++;  
  } 

mysql_close();
?>
<meta http-equiv="refresh" content="0;URL=import_save.php" />
<? }?>
<?php
mysql_free_result($chk_data);
?>