How to check the data for duplicates in xml

Question

Hi all,
I have an xml similar to the below. In that I need an xquery which can remove the tags for which the data is same. For example in the below xml for first <customer> first <address> the <houseno>
and the second <address>'s <houseno> is same in that case there should be only one <houseno> tag with the data in the output xml. Please check the Input XML and Output XML xml formats below .
I am able to get the OUtputxml but with the same <houseno> repeating. I am not able to find a way in which I can chk the data and stop the tag getting created in the output.
Could you please suggest me the ways in which I can do. It would be of great help for me. Thanks a ton in advance.
Input XML
<customers>
     <customer>
          <address>
               <houseno>212</houseno>
                <phone>121221</phone>
          </address>
          <address>
               <houseno>212</houseno>
               <phone>42334</phone>             
          </address>
     <customer>
     <customer>
          <address>
               <houseno>3243</houseno>
               <phone>6565</phone>
          </address>
          <address>
               <houseno>3434</houseno>
                <phone>78778</phone>
          </address>
     </customer>
</customers>
Output XML Expected
<customers>
<customer>
          <address>
               <houseno>212</houseno>
                <phone>121221</phone>
                  <phone>42334</phone>              
          </address>
     <customer>
<customer>
          <address>
               <houseno>3243</houseno>
               <phone>6565</phone>
               <houseno>3434</houseno>
                <phone>78778</phone>
          </address>
     </customer>
</customers>
Output XML Which I am getting
<customers>
<customer>
          <address>
               <houseno>212</houseno>
                <houseno>212</houseno>        
                <phone>121221</phone>
                  <phone>42334</phone>              
          </address>
     <customer>
<customer>
          <address>
               <houseno>3243</houseno>
               <phone>6565</phone>
               <houseno>3434</houseno>
                <phone>6565</phone>
          </address>
     </customer>
</customers>
Regards

Answer 1

First of all the desired output.
[quote]
<customers>
<customer>
          <address>
               <houseno>212</houseno>
                <phone>121221</phone>
                  <phone>42334</phone>              
          </address>
     <customer>
<customer>
          <address>
               <houseno>3243</houseno>
               <phone>6565</phone>
               <houseno>3434</houseno>
                <phone>78778</phone>
          </address>
     </customer>
</customers>
[/quote]
I don't think this is a very good choice and will be causing trouble no end in a future stage of using the data...
I would rather propose a better choice to my thinking like this.
[code]
<customers>
    <customer>
          <address>
               <house houseno="212">
                   <phone>121221</phone>
                   <phone>42334</phone>
               </house>
          </address>
     </customer>
    <customer>
        <address>
            <house houseno="3243">
                <phone>6565</phone>
            </house>
            <house houseno="3434">
                <phone>78778</phone>
            </house>
       </address>
  </customer></customers>
[/code]
In that case, this is capable of producing the regrouped output.
[code]
<customers>{
    let $doc:=doc("your_data.xml")
    for $customer in $doc/customers/customer
    return
    <customer>{
        for $houseno in distinct-values($customer/address/houseno)
        return
        <house houseno="{$houseno}">{
           for $phone in $customer/address[houseno=$houseno]/phone
           return
           <phone>{data($phone)}</phone>
        }</house>
    }</customer>
}</customers>
[/code]