.XQ file extension

This is the basic program to work with .XQ extension

Altova XMLSpy

Altova XMLSpy XML Query Language

Altova XMLSpy is the industry’s best-selling XML editor and XML development environment for modeling, editing, transforming, and debugging XML technologies. In addition to the world’s leading XML editor, XMLSpy includes a powerful graphical XML Schema editor that allows you to design complex schemas with ease... (more)

The program works with the following extensions: xml, fo, xq, rdf, spp, svg, vml, mml, dtd, wml, xdr, xql, xsd, tsd, biz, tld, mtx, jsp, cml, dcd, ent, xsl, rels, math, smil, vxml, wsdl, xslt, xhtml and xquery

.XQ extension is also supported by the following programs:

Oxygen XML Editor

Oxygen XML Editor XQuery Document

Edit, convert, and debug XML databases, files, and servers.
Stylus Studio

Stylus Studio

Stylus Studio 2006 XML Enterprise Edition is an advanced XML IDE.
XMLSPY 5 Enterprise Edition

XMLSPY 5 Enterprise Edition XML Query Language