Motivation

You have a list of items in an XML structure and you want to display a comma separated list of the values in an output string.

Method

XQuery provides the "string-join()" function that will take a sequence of items and a separator string and create and output string with the separator between each of the items. The format of the function is: string-join(nodeset, separator) where nodeset is a list of nodes and separator the string that you would like to separate the values with.

Sample Program

xquery version "1.0"; let $tags := <tags>  <tag>x</tag>  <tag>y</tag>  <tag>z</tag>  <tag>d</tag> </tags> return <results>  <comma-separated-values>{  string-join($tags/tag, ',')  }</comma-separated-values> </results>

Output

<results>  <comma-separated-values>x,y,z,d</comma-separated-values> </results>

Create a CSV file from XML

We will use two "string-join()" functions, one for all rows and one for each row. We will create one large string and then use the "response:stream()" function to return the results.

xquery version "1.0"; declare option exist:serialize "method=text media-type=text/csv omit-xml-declaration=yes"; (: The newline character used as a separator between lines :) let $nl := "&#10;" let $input := <rows>  <row>  <c1>Row1 Col1</c1>  <c2>Row1 Col2</c2>  <c3>Row1 Col3</c3>  <c4>Row1 Col4</c4>  </row>  <row>  <c1>Row2 Col1</c1>  <c2>Row2 Col2</c2>  <c3>Row2 Col3</c3>  <c4>Row2 Col4</c4>  </row>  <row>  <c1>Row3 Col1</c1>  <c2>Row3 Col2</c2>  <c3>Row3 Col3</c3>  <c4>Row3 Col4</c4>  </row>  <row>  <c1>Row4 Col1</c1>  <c2>Row4 Col2</c2>  <c3>Row4 Col3</c3>  <c4>Row2 Col4</c4>  </row> </rows> (: we construct a single string that has all the newlines and commas in the right places :) let $file-as-csv-string :=  string-join(  for $row in $input//row  return  string-join(  for $col in $row/*  return  $col/text()  , ',')  , $nl) (: set the HTTP response headers with the content type and file name :) let $set-content-type := response:set-header('Content-Type', 'text/csv') let $set-file-name := response:set-header('Content-Disposition', 'attachment; filename="my-table.csv"') (: There is no documentation on what the stream options are. http://exist-db.org/exist/apps/fundocs/view.html?uri=http://exist-db.org/xquery/response&location=java:org.exist.xquery.functions.response.ResponseModule :) return response:stream($file-as-csv-string, '')

Which returns:

 Row1 Col1,Row1 Col2,Row1 Col3,Row1 Col4 Row2 Col1,Row2 Col2,Row2 Col3,Row2 Col4 Row3 Col1,Row3 Col2,Row3 Col3,Row3 Col4 Row4 Col1,Row4 Col2,Row4 Col3,Row4 Col4

Discussion

The "string-join()" function takes two arguments, the first is the sequence of strings to be joined and the second is the separator.