Error saving MySQL PHP form information

What's happening:

I have a system that, when I finish filling out the form and save, does not save the changes appearing a alert of "saved without changes" and returning to the previous page.

What should happen:

When you try to save the form, the Saved script should appear successfully and return to the previous page.

As I do not master this language, I'm not finding out where the logic is responsible for recognizing that a field was changed and saving. I believe the error is in the form, since there is nothing wrong with the bank or the connection. Since I can not put the whole system here, I'll put some parts that I believe may be responsible for the error:

Find ID of what you want to change

<?php
// Busca valores no banco de dados para preenchimento do formulario para alterar
$id = $_GET['id'];
$sql = (" SELECT * FROM re WHERE id = '{$id}'");
$query=mysql_query($sql);
while ($campo = mysql_fetch_assoc($query)) {  
?>

part of the form

<div class="container">
    <form method="post" action="../std/update.php" enctype="multipart/form-data" name="re" class="formulario">
        <div class="container container-divisor">
            <h4>Descrição Re</h4>
            <div class="row">
                <input type="hidden" name="idnovo" id="idnovo" value="<?=$campo['id'];?>">
                <input type="hidden" name="dataedicao" id="dataedicao" value="<?php echo date('d/m/Y'); ?>">
                <div class="col-md-4">
                    <label for="datacriacao">Data</label>
                    <input type="text" class="form-control" name="datacriacao" id="dataCriacao" value="<?=$campo['datacriacao'];?>"127>
                </div>
          </div>
    </form>

In the page responsible for updating the database, the texts in js:

<?php
    if(mysql_affected_rows() > 0){
    ?>  
<script type="text/javascript">
    alert("Salvo com Sucesso !");
    window.history.go(-1);
</script>

<?php
        }
        else{
?>
<script type="text/javascript">
    alert("Salvo sem Modificações !");
    window.history.go(-1);
</script>
<?php           
        } 
mysql_close($conexao);
?>

The update page

<?php 
include ("conecta.php");

//coletando dados do formulario

    $id             =   $_POST["idnovo"]; 
    $dataedicao     =   $_POST["dataedicao"];
    $datacriacao    =   $_POST["datacriacao"];
    $statusgeral    =   $_POST["statusgeral"];
    $criadopor      =   $_POST["criadopor"];


// Inserir dados no banco
    $itens = $_POST['meti'];
//$_POST['meti'] as $itens
    if (!empty($itens)){
 $itens = implode(',', $_POST['meti']);
}



$up= mysql_query("UPDATE retex SET dataedicao = '$dataedicao', datacriacao = '$datacriacao', statusgeral = '$statusgeral', criadopor = '$criadopor' WHERE id = '$id' ");

?>
<?php
    if(mysql_affected_rows() > 0){
    ?>  
<script type="text/javascript">
    alert("Salvo com Sucesso !");
    window.history.go(-1);
</script>

<?php
        }
        else{
?>
<script type="text/javascript">
    alert("Salvo sem Modificações !");
    window.history.go(-1);
</script>
<?php           
        } 
mysql_close($conexao);
?>

I believe the form is not recognizing that a field has changed, but it is just a hypothesis. As I find out more things I edit.