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This article has been viewed 497 times.

Create a Variable with a Unique Sorted Node-Set

Written by Gregory Scot Collins

Monday, 8 May 2006, 7:27 AM

This article has been tested to work with the following products and versions. No guarantee of compatibility, with or without modification, is offered for products or versions other than those listed.

XML 1.0 (W3C)
XPath 1.0 (W3C)
XSLT 1.0 (W3C)

IN THIS ARTICLE:

In complex transforms it might be inconvenient-if not impossible-to accomplish your task without having a variable defined as a sorted node-set. This can be accomplished in two steps: First, a temporary variable is created that sorts the nodes. Second, a node-set is built from the temporary variable, while filtering for unique values. Both steps are required because the first variable does not constitute a node-set and subsequently cannot be used as such, and because we cannot perform sorting within the node-set() function. With our final node-set variable, we can accomplish our design.

The sorted variable can be defined globally at the top of your .xsl file as demonstrated here, or you can define it locally within a template. Let's create some sample files to demonstrate how to create and use a variable with a unique sorted node-set.

Create the source files

We need a simple XML file to transform. Copy the contents of Listing 1 into a text editor, and then save the file as Customers.xml.

<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="Customers.xsl"?>
 
<Customers>
    <Customer id="1" fname="Ben" lname="Harrisen" city="Midway"/>
    <Customer id="2" fname="Fenwick" lname="Hamford" city="Fairview"/>
    <Customer id="3" fname="Ronald" lname="Smitty" city="Salem"/>
    <Customer id="4" fname="Terri" lname="Wendell" city="Riverside"/>
    <Customer id="5" fname="Mark" lname="Franklin" city="Fairview"/>
    <Customer id="6" fname="Allison" lname="Harrisen" city="Riverside"/>
    <Customer id="7" fname="Harvey" lname="Jones" city="Centerville"/>
    <Customer id="8" fname="Alexis" lname="Wendell" city="Salem"/>
    <Customer id="9" fname="Ferdinand" lname="Beck" city="Riverside"/>
</Customers>

Listing 1. The Customers.xml file.

Copy the contents of Listing 2 into a text editor, and then save the file as Customers.xsl. Be sure to save it in the same folder as the Customers.xml file.

<?xml version="1.0" encoding="UTF-8"?>
<xsl:stylesheet version="1.0" 
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform" 
        xmlns:msxsl="urn:schemas-microsoft-com:xslt">
 
<xsl:strip-space elements="*"/>
<xsl:output method="html" indent="yes"/>
 
<xsl:variable name="TempSortedByCity">
    <xsl:for-each select="/Customers/Customer">
        <xsl:sort select="@city" data-type="text" order="ascending"/>
        <xsl:copy-of select="."/>
    </xsl:for-each>
</xsl:variable>
<xsl:variable name="UniqueCities" select="msxsl:node-set($TempSortedByCity)/*[not(@city = preceding-sibling::Customer/@city)]"/>
 
<xsl:template match="Customers">
    <b>SORTED UNIQUE CITIES:</b>
    <xsl:apply-templates select="$UniqueCities" mode="UniqueCities"/>
</xsl:template>
 
<xsl:template match="Customer" mode="UniqueCities">
    <div>
        <xsl:value-of select="@city"/>
    </div>
</xsl:template>
 
</xsl:stylesheet>

Listing 2. The Customers.xsl file.

Try it

Applying the transform to our XML results in the following output:

SORTED UNIQUE CITIES:

Centerville

Fairview

Midway

Riverside

Salem

Copyright ©2006 Braintrove. All rights reserved. This material may not be copied, published, broadcast, rewritten or redistributed. You may, however, use the techniques, along with any associated code and files in your development. This material is provided "AS IS" without warranty of any kind. You accept full responsibility and liability for any and all results associated with use of this material.

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		List of Figures
	Listing 1 - The Customers.xml file.
	Listing 2 - The Customers.xsl file.

		See Also
	Click to view Braintrove article: Create a Variable with a Sorted Node-Set Written by Gregory Scot Collins Tuesday, 2 May 2006, 10:02 AM Products: XML, XPath and XSLT Easily create and use a variable with a sorted node-set. Create a Variable with a Sorted Node-Set

		Article Tags
	Filters msxsl:node-set node-set preceding-sibling Sorting Transforms Variables XML XPath xsl:sort xsl:variable XSLT

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