• Chapter 1: Getting Started with Stylus Studio®
• Chapter 2: Editing and Querying XML
• Chapter 3: Converting Non-XML Files to XML
• Chapter 4: Working with XSLT
• Chapter 5: Creating XSLT Using the XSLT Mapper
• Chapter 6: Debugging Stylesheets
• Chapter 7: Defining XML Schemas
• Chapter 8: Defining Document Type Definitions
• Chapter 9: Writing XPath Expressions
• Chapter 10: Working with XQuery in Stylus Studio
  • Getting Started with XQuery in Stylus Studio
  • An XQuery Primer
  • Understanding FLWOR Expressions
    • Simple XQuery FLWOR Expressions
    • The Principal Parts of an XQuery FLWOR Expression
    • Other Parts of the XQuery FLWOR Expression
    • Grouping
  • Building an XQuery Using the Mapper
  • Working with the XQuery collection() Function
  • Debugging XQuery Documents
  • Creating an XQuery Scenario
  • Generating XQuery Documentation
  • Using XQuery to Invoke a Web Service
  • Generating Java Code for XQuery
• Chapter 11: Composing Web Service Calls
• Chapter 12: Accessing Relational Data as XML
• Chapter 13: Building XML Pipelines
• Chapter 14: Publishing XML Data
• Chapter 15: Integrating with Third-Party File Systems
• Chapter 16: Extending Stylus Studio
• Chapter 17: The Stylus Studio Java API
• Chapter 18: Stylus Studio GUI Reference

Home > Online Product Documentation > Table of Contents > Simple XQuery FLWOR Expressions

Simple XQuery FLWOR Expressions

The simplest XQuery FLWOR expression might be something like this:

              for $v in $doc//video return $v
               

            

This returns all of the video elements in $doc.

We can add a bit of substance by adding XQuery where and return clauses:

              for $v in $doc//video
               

              where $v/year = 1999
               

              return $v/title
               

            

This returns all of the titles of videos released in 1999.

If you know SQL, that XQuery probably looks reassuringly similar to the equivalent SQL statement:

              SELECT v.title 
               

              FROM video v 
               

              WHERE v.year = 1999
               

            

And if you know XPath, you might be wondering why our XQuery cannot be written as this:

              $doc//video[year=1999]/title
               

            

Well, you can. This XPath expression is completely equivalent to the FLWOR expression above, and furthermore, it is a legal XQuery query. In fact, every legal XPath expression is also legal in XQuery. Thus the first query in this section can be written as:

              $doc//video
               

            

Which style you prefer seems to depend on where you are coming from: if you have been using XML for years, especially XML with a deep hierarchy as found in "narrative" documents, then you will probably be comfortable with path expressions. But if you are more used to thinking of your data as representing a table, then the FLWOR style might suit you better.

As you will see, FLWOR expressions are a lot more powerful than path expressions when it comes to doing joins. But for simple queries, the capabilities overlap and you have a choice. Although it might be true that in SQL every query is a SELECT statement, it is not so that in XQuery every query has to be a FLWOR expression.