Responsive Table in Bootstrap with columns with same width - php

Question

This is the code, and as written in the title, I'm trying to have each column with the same width:
<div class="table-responsive">
<table class="table table-striped table-hover">
<thead>
<tr>
<th>N°</th>
<th>Data</th>
<th>Compratore</th>
<th>Venditore</th>
<th>Merce</th>
<th>Quantita'</th>
<th>Prezzo</th>
<th>Pagamento</th>
<th>Azioni</th>
</tr>
</thead>
<tbody>
<?php
$result = query("SELECT numero_contratto, anno_contratto, data, C.denominazione as compratore, V.denominazione as venditore, merce, quantita, info_quantita, prezzo, info_prezzo, pagamento FROM Contratti, Societa V, Societa C WHERE compratore = C.id_societa and venditore = V.id_societa ORDER BY data DESC", $conn);
foreach($result as $r)
{
?>
<tr>
<td>
<?php echo $r['numero_contratto']."/".$r['anno_contratto']; ?>
</td>
<td>
<?php
$data = explode("-", $r['data']);
echo $data[2]."-".$data[1]."-".$data[0];
?>
</td>
<td>
<?php echo $r['compratore']; ?>
</td>
<td>
<?php echo $r['venditore']; ?>
</td>
<td>
<?php echo $r['merce']; ?>
</td>
<td>
<?php echo $r['quantita']." ".$r['info_quantita']; ?>
</td>
<td>
<?php echo $r['prezzo']." ".$r['info_prezzo']; ?>
</td>
<td>
<?php echo $r['pagamento']; ?>
</td>
<td>
<span class="glyphicon glyphicon-remove"></span>
</td>
</tr>
<?php
}
?>
</tbody>
</table>
</div>
And this is the output on my web page:
But if you see this Fiddle with static values putted into the table, the problem doesn't show!
http://jsfiddle.net/brVa9/1/
So the problem is inside the db schema or structure.
What I should do to have all the columns with the same width?