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XQuery, 2nd Edition by Priscilla Walmsley

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Appendix A. Built-in Function Reference

This appendix describes the functions that are built into XQuery. Table A-1 lists all the built-in functions by subject for easy reference. In addition to a brief sentence explaining the purpose of the function, each function is described by the following characteristics:

  • “Signature” lists the parameters and their types, and the return type of the function.

  • “Usage Notes” covers the function in more detail.

  • “Special Cases” lists error conditions and other unusual situations.

  • “Example(s)” provides one or more example function calls with their return values.

  • “Related Functions” lists names of related functions.

Most of the built-in functions are in the XPath Functions Namespace, http://www.w3.org/2005/xpath-functions. These do not need to be prefixed when called in a query, so they are listed in this appendix without a prefix. Some people prefer to use the prefix fn with these functions, which works because the XPath Functions namespace is predeclared with the prefix fn.

Other functions in this appendix are shown with the prefixes math, array, and map. These three namespace prefixes are not predeclared. To use functions in these namespaces, declare the namespaces in your query prolog, for example:

declare namespace math = "http://www.w3.org/2005/xpath-functions/math";
declare namespace array = "http://www.w3.org/2005/xpath-functions/array";
declare namespace map = "http://www.w3.org/2005/xpath-functions/map";

Many of the built-in functions have more than ...

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