XQuery is designed to query XML data -not just XML files, but anything that can appear as XML, including databases. XQuery uses XPath expression syntax to address specific parts of an XML document. It supplements this with a SQL -like "FLWOR expression" for performing joins. A FLWOR expression is constructed from the five clauses after which it is named: FOR, LET, WHERE, ORDER BY, RETURN.
XQuery is supported by all the major database engines ( IBM, Oracle, Microsoft, etc.)
XQuery will become a W3C standard - and developers can be sure that the code will work among different products