XQuery to filter a dynamic list of strings

Question

I am looking for some recommendations to make me move in the right direction. I am using xquery to return an XML document that is similar to the xml below.

<myDoc>
  <myElements id="1">
    <myElement key="one">aaa</myElement>
    <myElement key="two" >bbb</myElement>
    <myElement key="three">ccc</myElement>
  </myElements>
  <myElements id="2">
    <myElement key="one">ddd</myElement>
    <myElement key="two" >eee</myElement>
    <myElement key="three">fff</myElement>
  </myElements>
</myDoc>

I am trying to return a document with only specific lines <myElements>whose key is specified. For example, if the keys are "one" and "three", the resulting xml should look like this:

<myDoc>
  <myElements id="1">
    <myElement key="one">aaa</myElement>
    <myElement key="three">ccc</myElement>
  </myElements>
  <myElements id="2">
    <myElement key="one">ddd</myElement>
    <myElement key="three">fff</myElement>
  </myElements>
</myDoc>

Is it possible? Any advice that could point me in the right direction would be greatly appreciated.

Answer 1

This kind of problem is much more suitable for XSLT, but it can also be solved in XQuery.

Something like this :

let $vKeys := ('one', 'three')
 return
   element {name(/*)}
     {for $child in /*/*
       return
        element {name($child)} 
          {for $att in $child/@*
            return
             attribute {name($att)} {$att},
           for $grandchild in $child/myElement[@key=$vKeys]
             return $grandchild
          }
     }

, XML-:

<myDoc>
  <myElements id="1">
    <myElement key="one">aaa</myElement>
    <myElement key="two" >bbb</myElement>
    <myElement key="three">ccc</myElement>
  </myElements>
  <myElements id="2">
    <myElement key="one">ddd</myElement>
    <myElement key="two" >eee</myElement>
    <myElement key="three">fff</myElement>
  </myElements>
</myDoc>

, :

<myDoc>
   <myElements id="1">
      <myElement key="one">aaa</myElement>
      <myElement key="three">ccc</myElement>
   </myElements>
   <myElements id="2">
      <myElement key="one">ddd</myElement>
      <myElement key="three">fff</myElement>
   </myElements>
</myDoc>