How get unique option fileds in a dynamic dropdown box

I'm trying to get single select options in a dropdown menu.

The data is coming from two database.

My CFQuery looks like

<cfquery name="related" datasource="ISSUE">
SELECT sparprod
FROM Related
where Active = 'Yes'
union all
select sparprod from TBL_issue
WHERE issue_number = <cfqueryparam value="#URL.issue_number#" cfsqltype="cf_sql_numeric">
ORDER BY sparprod ASC
</cfquery>

  <td>

        <select name="sparprod" id="sparprod" >

          <cfoutput query="related">

            <option value="#related.sparprod#" <cfif (isDefined("rs_issue.sparprod") AND related.sparprod EQ rs_issue.sparprod)>selected="selected"</cfif>>#related.sparprod#</option>

          </cfoutput>

        </select>

And the output in the dropdown box looks like

PRODUCTS

SPARES

SPARES

HOW can i have only ONE TIME Spares.

I've got this problem with all my dynamic dropdown boxes.

Thanks

For your help in advance

Klaas