Group repeated data from a given column

Question

I need to select and group the items, but as I have searched, my query will come from a database selected by a variable via post, and I will list the columns that are in a while coming via post from a variable also.

The problem is to group the column that is in while and its results !<br><br> (I add the columns dynamically so I can list "easily" later in select, recording as field1, field2 and so on)

In the case of the image I am selecting by a specific field and not by the variable coming via POST. The product listing, side, etc... ta listed below with the columns named field1, field2, etc.

ex.:

    <p>:: Cadatre a Ultima Compra do Cliente</p>
<?php
    $fila = 'grafica';//$_POST['bd'];
    $pega = $fila.'_lista';
$mostrando = mysql_query("SELECT * FROM $pega order by cod asc " )or die (mysql_error());
    while ($vendo = mysql_fetch_array($mostrando)) {
$campo = $vendo['campo'];

        echo '<div class="_cliente">'.$campo.'</div>';
    }   

    ?>

    <select name="prods" class="input_prod" style="clear: left;">
<?php   
        $prod = mysql_query("SELECT campo1 FROM $fila group by campo1 order by cod asc ") or die(mysql_error());    
    while ($listar = mysql_fetch_array($prod)){

        $campo1 = $listar['campo1'];

        echo '<option value="'.$campo1.'" title="'.$campo1.'">'.$campo1.'</option>';
    }
        ?>

</select>

this example above is as I listed in the sent image, but I need to make a SELECT dynamically.