displaying sql results in dropdown menus

I'm trying to get dropdown menus of values from a xml file, which is
the  result of a SQL request:

            <idattr>sql:id_collection</idattr>
            <idattr>sql:libelle_collection</idattr>

            <td>
                <rowset xmlns="http://apache.org/cocoon/SQL/2.0"
nrofrows="12">
                <row>
                    <id_collection>1</id_collection>
                    <libelle_collection>CIP</libelle_collection>
                </row>
                <row>
                    <id_collection>2</id_collection>
                    <libelle_collection>Champignons</libelle_collection>
                </row>
                <row>
                    <id_collection>3</id_collection>
                    <libelle_collection>IEBC</libelle_collection>
                </row>

            </rowset>
            </td>

(I don't directly put the attributes' id s in the xsl because I want  a
generalized file,
which could work for any request' s result)

    <xsl:variable name="idattr1" select="../../idattr[1]"/>
    <xsl:variable name="idattr2" select="../../idattr[2]"/>

     <select size="1" name="">
           <option value="-1">- Silectionnez :</option>

            <xsl:for-each select="sql:row">
                <option  value= "$idattr1">
               <xsl:value-of select="$idattr2"/>
              </option>
             </xsl:for-each>
        </select>

...
 All I manage to obtain is :

<td>Collection</td>
<td>
<select name="" size="1">
<option value="-1">- Silectionnez :</option>
<option value="$idattr1">sql:libelle_collection</option>
<option value="$idattr1">sql:libelle_collection</option>
<option value="$idattr1">sql:libelle_collection</option>
</select></td>

instead of the dropdown list with the values INSIDE the "
libelle_collection"  tags...
Perhaps it is a problem with Cocoon's SQL Transformer...