FLWOR

FLWOR stands for:
For–Let–Where–Order by–Return

It is a powerful expression construct used in XQuery (and XPath 2.0+) to query and transform XML data. Think of it as the “SQL for XML”, allowing you to iterate, filter, sort, and return complex results from XML documents.

Components

Clause	Purpose
For	Iterates over a sequence of items (similar to SQL’s FROM).
Let	Binds a variable to a value or expression.
Where	Filters items based on a condition.
Order by	Sorts the output (optional).
Return	Defines what to output for each item in the final result.

Not all clauses are required, but, at a minimum, for and return are used.

Syntax Example

XML Input

<books>
  <book>
    <title>1984</title>
    <author>George Orwell</author>
    <year>1949</year>
  </book>
  <book>
    <title>Brave New World</title>
    <author>Aldous Huxley</author>
    <year>1932</year>
  </book>
</books>

FLWOR Query (XQuery)

for $b in /books/book
where $b/year > 1935
order by $b/title
return <result>{$b/title}</result>

Output

<result>1984</result>

Use Cases

• Extracting and transforming XML data.
• Generating new XML structures from existing ones.
• Filtering and sorting large XML datasets.
• Querying XML-based data sources (like configuration files, APIs, or XML databases).