XQuery Syntax

XQuery elements, attributes, and variables must be valid XML names and follow case sensitivity.

XQuery Syntax Rules

  • XQuery follows case-sensitivity.
  • XQuery elements, attributes, and variables must be valid XML names.
  • An XQuery string value can be in single or double quotes.
  • An XQuery variable is defined with a $ followed by a name, for example:. $bookstore
  • XQuery comments are delimited by (: and :), e.g. (: XQuery Comment :)


Let's take an XML file 'books.xml' having the following data:

<book category="Romantic">
<title lang="en">If she loves me</title>
<author>Ajeet Kumar</author>
<book category="children">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<book category="programming">
<title lang="en">Let's C</title>
<author>Yashwant Kanetkar</author>

XQuery Conditional Expressions

The "If-Then-Else" conditional statement is allowed in XQuery.

XQuery statement:


for $x in doc("books.xml")/bookstore/book
return if ($x/@category="CHILDREN")
then <child>{data($x/title)}</child>
else <adult>{data($x/title)}</adult>

How to run

Create a Java based XQuery executor program to read the books.xqy, passes it to the XQuery expression processor, and executes the expression. After that the result will be displayed.


import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import javax.xml.xquery.XQConnection;
import javax.xml.xquery.XQDataSource;
import javax.xml.xquery.XQException;
import javax.xml.xquery.XQPreparedExpression;
import javax.xml.xquery.XQResultSequence;
import com.saxonica.xqj.SaxonXQDataSource;
public class XQueryTester {
   public static void main(String[] args){
      try {
      catch (FileNotFoundException e) {
      catch (XQException e) {
   private static void execute() throws FileNotFoundException, XQException{
      InputStream inputStream = new FileInputStream(new File("courses.xqy"));
      XQDataSource ds = new SaxonXQDataSource();
      XQConnection conn = ds.getConnection();
      XQPreparedExpression exp = conn.prepareExpression(inputStream);
      XQResultSequence result = exp.executeQuery();
       while (result.next()) {

Execute XQuery against XML

Put the above three files to a same location. We put them on desktop in a folder name XQuery6.

Compile XQueryTester.java using console. You must have JDK 1.5 or later installed on your computer and classpaths are configured.


javac XQueryTester.java


java XQueryTester


XQUERY Syntax 1

XQuery Comparisons

There are two types for comparing values in XQuery.

  1. General Comparison: =, !=, <, <=, >, >=
  2. Value Comparison: eq, ne, lt, le, gt, ge

Difference between general comparison and value comparison

It can be explained by an example. The following expression returns true if any q attributes have a value greater than 100.

$bookstore//book/@q > 100

The following expression returns true if there is only one q attribute returned by the expression, and its value is greater than 10. If more than one q is returned, an error occurs:

$bookstore//book/@q gt 100
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