XQuery Introduction

From http://www.w3schools.com (Copyright Refsnes Data)

# Introduction to XQuery

The best way to explain XQuery is to say that XQuery is to XML what SQL is to database tables.

XQuery is designed to query XML data - not just XML files, but anything that can appear as XML, including databases.

## What You Should Already Know

Before you continue you should have a basic understanding of the following:

- HTML / XHTML
- XML / XML Namespaces
- XPath

If you want to study these subjects first, find the tutorials on our Home page.

## What is XQuery?

- XQuery is the language for querying XML data
- XQuery for XML is like SQL for databases
- XQuery is built on XPath expressions
- XQuery is supported by all the major database engines (IBM, Oracle, Microsoft, etc.)
- XQuery is a W3C Recommendation

## XQuery is About Querying XML

XQuery is a language for finding and extracting elements and attributes from XML documents.

Here is an example of a question that XQuery could solve:

"Select all CD records with a price less than $10 from the CD collection stored in the XML document called cd_catalog.xml"

## XQuery and XPath

XQuery 1.0 and XPath 2.0 share the same data model and support the same functions and operators. If you have already studied XPath you will have no problems with understanding XQuery.

You can read more about XPath in our XPath Tutorial.

## XQuery - Examples of Use

XQuery can be used to:

- Extract information to use in a Web Service
- Generate summary reports
- Transform XML data to XHTML
- Search Web documents for relevant information

## XQuery is a W3C Recommendation

XQuery is compatible with several W3C standards, such as XML, Namespaces, XSLT, XPath, and XML Schema.

XQuery 1.0 became a W3C Recommendation January 23, 2007.

To read more about the XQuery activity at W3C, please read our W3C Tutorial.

From http://www.w3schools.com (Copyright Refsnes Data)