A User-Defined Function, UDF, is a way to create functions that can be used within an SQL statement, and thus add to the set of built-in SQL functions supplied with DB2. For example, the XML Extender creates the XMLCLOBFromFile UDF to insert XML data from a file into an XMLCLOB column.

XML Extender

The XML Extender, extends the capability of DB2 to work with data in XML documents. This means that you can store, update, and retrieve XML documents from DB2 tables with the help of the XML Extender.

A summary of the facilities that the XML Extender provides:

￿Stores and retrieves as-isXML documents in DB2 table columns

￿Stores the elements and attributes of an XML document in separate tables, or separates columns within the same table

￿Composes an XML document with data that is residing in existing DB2 tables.

The XML Extender performs a series of tasks in order to enable a DB2 database and table for XML data. These tasks include:

￿Create a set of tables for its own use

￿Create User Defined Types (UDT) to accommodate XML data in table columns

￿Create Used Defined Functions (UDF) and stored procedures (SP) to manipulate XML data

￿Create triggers to maintain the data integrity for the XML data spread across multiple tables

Figure 6-13 shows an overview of the XML Extender.

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IBM Version 5 manual shows an overview of the XML Extender