🔃 XSLT <xsl:sort> – Sort XML Nodes in Your Transformation

🧲 Introduction – Why Learn <xsl:sort>?

In many XML applications, you need to sort items before displaying them—by name, price, date, or ID. The <xsl:sort> element in XSLT allows you to do just that. It works inside <xsl:for-each> or <xsl:apply-templates> to organize node sets during transformation output.

🎯 In this guide, you’ll learn:

• How <xsl:sort> works and where to use it
• Syntax for sorting by text, number, or attribute
• Sort ascending or descending
• Practical examples with <xsl:for-each> and <xsl:apply-templates>

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🧾 Syntax of <xsl:sort>

<xsl:sort select="XPathExpression" data-type="text|number" order="ascending|descending"/>

• select: XPath expression to use as the sort key
• data-type: Optional – text (default) or number
• order: Optional – ascending (default) or descending

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📄 Sample XML

<catalog>
  <book id="102">
    <title>XSLT Advanced</title>
    <price>599</price>
  </book>
  <book id="101">
    <title>Learn XSLT</title>
    <price>499</price>
  </book>
  <book id="103">
    <title>XSLT for Beginners</title>
    <price>399</price>
  </book>
</catalog>

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🔠 Example – Sort by Title (Alphabetical)

<xsl:for-each select="catalog/book">
  <xsl:sort select="title" data-type="text" order="ascending"/>
  <p><xsl:value-of select="title"/></p>
</xsl:for-each>

✅ Output:

• Learn XSLT
• XSLT Advanced
• XSLT for Beginners

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💲 Example – Sort by Price (Lowest to Highest)

<xsl:for-each select="catalog/book">
  <xsl:sort select="price" data-type="number" order="ascending"/>
  <p><xsl:value-of select="title"/> – ₹<xsl:value-of select="price"/></p>
</xsl:for-each>

✅ Output:

• XSLT for Beginners – ₹399
• Learn XSLT – ₹499
• XSLT Advanced – ₹599

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🔁 Example – Sort by Attribute (@id)

<xsl:for-each select="catalog/book">
  <xsl:sort select="@id" data-type="number"/>
  <p><xsl:value-of select="title"/></p>
</xsl:for-each>

✅ Sorts books based on their id attributes numerically.

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🔄 Using <xsl:sort> with <xsl:apply-templates>

<xsl:apply-templates select="catalog/book">
  <xsl:sort select="title"/>
</xsl:apply-templates>

✅ Applies sorting when template rules are used instead of inline output.

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⚠️ Things to Remember

• <xsl:sort> must appear first inside <xsl:for-each> or <xsl:apply-templates>
• Default sort is text and ascending
• Use data-type="number" for numerical values (e.g., prices, ratings, IDs)

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✅ Best Practices for <xsl:sort>

• ✔️ Use data-type="number" for numeric accuracy
• ✔️ Always sort before value-of or output rendering
• ✔️ Chain multiple <xsl:sort> elements to apply secondary sorting
• ❌ Don’t forget to check if values exist—missing values may cause blank sorting

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📌 Summary – Recap & Next Steps

XSLT <xsl:sort> makes your transformations dynamic and organized. Whether you’re generating a product list, an article feed, or a data report, sorting nodes lets you present XML data clearly and professionally.

🔍 Key Takeaways:

• Use <xsl:sort> inside loops or templates to control output order
• Supports text and number sorting
• Combine with attributes, values, or child elements as sort keys

⚙️ Real-world relevance: Used in sorted report generation, catalog listings, content filters, price lists, and feeds.

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❓ FAQs – XSLT <sort>

❓ Can I sort by element text?
✅ Yes. Use <xsl:sort select="title"/> or similar.

❓ Can I sort by multiple criteria?
✅ Yes. Use multiple <xsl:sort> tags in order of priority.

❓ What happens if data-type is missing?
✅ Defaults to text sort.

❓ Can I use @attribute in sort?
✅ Absolutely. Use @id, @price, etc.

❓ Can I reverse the sort order?
✅ Yes. Use order="descending".

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