XQuery

XQuery (XML Query) is a query language and functional programming language designed to query and transform collections of structured and unstructured data, primarily in the form of XML. It also supports text data and, through implementation-specific extensions, other formats like binary and relational data.

The language was developed by the XML Query working group of the W3C, with version 1.0 becoming a W3C Recommendation in January 2007. XQuery development is closely coordinated with the development of XSLT by the XSL Working Group. Both groups jointly maintain XPath, a shared component of XQuery and XSLT. XQuery extends XPath with features like FLWOR (For, Let, Where, Order by, Return) expressions, making it semantically similar to SQL but optimized for hierarchical rather than relational data.

XQuery 3.1, published in March 2017, added support for JSON and introduced maps, arrays, and additional higher-order functions, significantly expanding the language's capabilities for modern data processing.

XQuery is implemented by many database systems, XML databases, and XML processors, including BaseX, eXist, MarkLogic, Saxon, and Berkeley DB XML, making it a cornerstone technology for processing XML data in enterprise software applications.