Here’s how to eliminate duplicate elements using XSLT

Hi Folks,

[This is a summary of yesterday's discussion, for the archives.]

I have an XML document that consists of <row> elements:

<Document>
    <row>
        <x>1</x>
       <y>2</y>
    </row>
    <row>
        <x>3</x>
       <y>4</y>
    </row>
    <row>
        <x>1</x>
       <y>2</y>
    </row>
</Document>

I want to eliminate duplicate rows. row[1] and row[3] have the same elements
with the same values. They are duplicates. I only want one of them.

Michael Kay responded:

In this situation, you can use grouping:

<xsl:for-each-group select="row" group-by="x, y" composite="yes">
      <xsl:sequence select="current-group()[1]"/>
</xsl:for-each>

Roger: Wow! That simple for-loop is doing an enormous amount of work 
grouping elements by their content, iterating over the groups, selecting the
first of each group (thus, deleting the duplicates). That is beautiful code.
Thank you Michael.