XML - XML XQuery

What is XQuery?

XQuery stands for XML Query Language. It is a powerful language used to search, filter, and extract data from XML documents, just like SQL is used to query databases. If you have a large XML file and want to find only certain information from it—like all students with grade "A"—XQuery helps you do that easily.

Why do we need XQuery?

XML is great for storing data, but it can be very large and complex. Just like we use Google to search the internet, we use XQuery to search inside XML files. It can find specific values, match patterns, sort data, join data from multiple XML files, and even format the result.

Let’s say you have an XML file with hundreds of students. If you only want to find students who passed, or list their names in alphabetical order, XQuery can do all that quickly.

What can XQuery do?

Select specific elements (like names, grades, or books)
Filter data (e.g., students with grade A)
Sort results (e.g., alphabetically)
Loop through XML elements
Join data from different XML files
Create new XML or HTML output

Simple Example

Here’s an example XML:

<students>
  <student>
    <name>Ali</name>
    <grade>A</grade>
  </student>
  <student>
    <name>Sara</name>
    <grade>B</grade>
  </student>
</students>

A basic XQuery to get names of students with grade A:

for $x in /students/student
where $x/grade = 'A'
return $x/name

This code says:

Look at every <student> in <students>.
Only keep the ones with <grade>A</grade>.
Return the <name> of those students.

XQuery vs XPath

You may have heard of XPath, which is used to navigate XML. XQuery uses XPath inside it to move through XML, but adds more features like loops, conditions, sorting, and generating new output. So you can think of XQuery as XPath with superpowers.

Where is XQuery used?

In web applications that use XML for data
To query XML databases
In data transformation tools
In APIs and Web Services that return XML data
For report generation from large XML files