Applying Muenchian grouping for a simple XML with XSLT

Question

How does Muenchian grouping work in details?

I have a simple XML document generated from a database:

<CLIENTS>
    <CLIENT>
       <NAME>John</NAME>
       <ACCOUNT_NUMBER>1424763562761</ACCOUNT_NUMBER>
       <LAST_USED>2012-10-03</LAST_USED>
       <AMOUNT>5000</AMOUNT>

    </CLIENT>
    <CLIENT>
       <NAME>John</NAME>
       <ACCOUNT_NUMBER>543667543732</ACCOUNT_NUMBER>
       <LAST_USED>2012-10-02</LAST_USED>
       <AMOUNT>10000</AMOUNT>
    </CLIENT>
       ...

I'd like to group by the name node. How can I the desired ouput to be the following?

<ClIENTS>
    <CLIENT>
        <NAME>John</NAME>
        <ACCOUNT>
           <ACCOUNT_NUMBER>1424763562761</ACCOUNT_NUMBER>
           <LAST_USED>2012-10-03</LAST_USED>
           <AMOUNT>5000</AMOUNT>
        </ACCOUNT>
        <ACCOUNT>
           <ACCOUNT_NUMBER>543667543732</ACCOUNT_NUMBER>
           <LAST_USED>2012-10-03</LAST_USED>
           <AMOUNT>10000</AMOUNT>
        </ACCOUNT>
       ....
</CLIENTS>

Answer 1

Read www.jenitennison.com/xslt/grouping/muenchian.xml, for a help with the code define a key

<xsl:key name="client-by-name" match="CLIENT" use="NAME"/>

then use templates as

<xsl:template match="@* | node()">
  <xsl:copy>
    <xsl:apply-templates select="@* | node()"/>
  </xsl:copy>
</xsl:template>


<xsl:template match="CLIENTS">
  <xsl:copy>
    <xsl:apply-templates select="CLIENT[generate-id() = generate-id(key('client-by-name', NAME)[1])]" mode="group"/>
  <xsl:copy>
</xsl:template>

<xsl:template match="CLIENT" mode="group">
  <xsl:copy>
    <xsl:copy-of select="NAME"/>
    <xsl:apply-templates select="key('client-by-name', NAME)"/>
  </xsl:copy>
</xsl:template>

<xsl:template match="CLIENT">
  <ACCOUNT>
    <xsl:apply-templates select="node()[not(self::NAME)]"/>
  </ACCOUNT>
</xsl:template>

[edit] If you want to use XSLT 2.0 then of course you don't need Muenchian grouping, instead you use

<xsl:template match="@* | node()">
  <xsl:copy>
    <xsl:apply-templates select="@* , node()"/>
  </xsl:copy>
</xsl:template>

<xsl:template match="CLIENTS">
  <xsl:copy>
    <xsl:for-each-group select="CLIENT" group-by="NAME">
      <CLIENT>
        <xsl:apply-templates select="NAME, current-group()"/>
      </CLIENT>
    </xsl:for-each-group>
  </xsl:copy>
</xsl:template>

<xsl:template match="CLIENT">
  <ACCOUNT>
    <xsl:apply-templates select="node() except NAME"/>
  </ACCOUNT>
</xsl:template>