DB2 XQuery concepts
The following topics introduce basic XQuery concepts and
describe how XQuery works with a DB2 database.
Type system
XQuery is a strongly-typed language in which the operands
of various expressions, operators, and functions must conform to expected
types. The type system for DB2 XQuery
includes the built-in types of XML Schema and the predefined types
of XQuery.
Prolog
The prolog is series of declarations that
define the processing environment for a query. Each declaration in
the prolog is followed by a semicolon (;). The prolog is an optional
part of the query; a valid query can consist of a query body with
no prolog.
Expressions
Expressions are the basic building blocks of a query. Expressions
can be used alone or in combination with other expressions to form
complex queries. DB2 XQuery
supports several kinds of expressions for working with XML data.
Built-in functions
DB2 XQuery provides
a library of built-in functions for working with XML data. These built-in
functions include XQuery-defined functions and DB2-defined functions.
Regular expressions
A regular expression is a sequence of characters that act
as a pattern for matching and manipulating strings. Regular expressions
are used in the following XQuery functions: fn:matches, fn:replace,
and fn:tokenize. DB2 XQuery
regular expression support is based on the XML schema regular expression
support as defined in the W3C Recommendation XML Schema Part 2:
Datatypes Second Edition with extensions as defined by W3C Recommendation XQuery
1.0 and XPath 2.0 Functions and Operators.
Limits
DB2 XQuery has size
limits and limits for data types.
DB2 Version 9.7 for Linux, UNIX, and Windows