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How to Sort XML by Attributes Using XSLT

How to sort XML by attributes using XSLT?

Create an XML document.

<?xml version="1.0"?>
<?xml-stylesheet type="text/xsl" href="sort.xsl"?>
<books>
   <book>  
        <title ISBN="0321173481" author="Michael R. Sweet">
	OpenGL Programming Guide Fourth Edition</title>		
	<publisher>Addison-Wesley</publisher>
	<year>2004</year>
   </book>
   <book>
	<title ISBN="0849371643" author="Gerald Farin">
	Curves and Surfaces for CAGD: A Practical Guide</title>
	<publisher>Academic Press</publisher>
	<year>2002</year>
   </book>
   <book>
	<title ISBN="1558606696" author="David Rogers">
	An Introduction to NURBS: With Historical Perspective</title>
	<publisher>Academic Press</publisher>
	<year>2001</year>
   </book>
   <book>
	<title ISBN="1568810849" author="Gerald Farin">
	NURBS: From Projective Geometry to Practical Use</title>
	<publisher>A K Peters</publisher>
	<year>1999</year>
   </book>
</books>

Create an XSL stylesheet.

<?xml version="1.0"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<xsl:output method="html" encoding="UTF-8"/>
<xsl:template match="/">
<html>
<head><title>Books</title>
</head>
<body>
<table width="100%" border="1">
 <THEAD>
   <TR>
     <TD width="40%"><B>Title</B></TD>
     <TD width="10%"><B>Publisher</B></TD>
   </TR>
 </THEAD> 
 <TBODY>
   <xsl:for-each select="books/book">
     <xsl:sort select="title/@ISBN" />
     <xsl:sort select="title/@author" />
   <TR>	
     <TD width="40%"><xsl:value-of select="title/@ISBN" /></TD>   
     <TD width="10%"><xsl:value-of select="title/@author" /></TD>
   </TR>
  </xsl:for-each>
 </TBODY>
</table>
</body>
</html>
</xsl:template>
</xsl:stylesheet>

In the example, the ISBN and author attributes are held within the <title> which is a child element of <book> so we refer to the attributes through their parent element. <xsl:sort select="title/@ISBN" />.

<xsl:sort> must be placed right after the <xsl:for-each> or <xsl:apply-templates> elements.

<xsl:sort select="title/@ISBN" /> sorts each <title> element attribute value. The default sort mode is ascending and the default data-type is text.

When sorting numbers, make sure to set the data-type attribute of <xsl:sort> to a number.

<xsl:sort select="ISBN" data-type="number"> will sort the numbers starting from the smallest.

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