XQuery

XQuery is a query and functional programming language designed for querying and transforming collections of structured XML data. It is a W3C standard used to retrieve and manipulate information from XML documents, and to operate on XML in databases, document stores, and data feeds.

XQuery is built on XPath and the XML Path Model, and it operates on the XML Data Model (XDM). It emphasizes FLWOR expressions—for, let, where, order by, return—a concise, declarative style for querying, transforming, and constructing new XML structures from existing data.

Versions of XQuery have evolved from XQuery 1.0 (a W3C Recommendation) to later revisions that add more functional features, higher‑order functions, and type options such as maps and arrays in XQuery 3.x. The XQuery Update Facility provides standardized support for modifying XML data; it is a separate specification used in conjunction with XQuery.

XQuery is implemented in a range of XML processing engines and databases, including BaseX, eXist-db, Saxon, MarkLogic, and Sedna. It is widely used for data extraction, transformation, and integration of XML documents, as well as for exporting results to other formats and for querying XML-based web services.