XML Data

DB2 9.1 XML/XQuery support

I investigated the XML and XQuery support in IBM's RDBMS (strictly speaking, a hybrid relational/XML DBMS), DB2 9.1 (as of 2009-10-31, I think the latest DB2 release is 9.7). The XML tooling in DB2 9.1 is called pureXML.

DB2 9.1 provides support for 'XML' data type in SQL (which is now part of the ISO/IEC SQL specification). We can now define table columns, of type 'XML' in DB2. This makes it possible to store an entire XML document in a particular field of a relational DB2 table. Within this 'XML' field, an XML document is stored in it's native hierarchical form (the XML is stored in a native XML store, whereas the pointer to the XML document is kept in the field). This approach of XML storage into relational tables, is different to traditional shredding of XML documents into the relational tables. Shredding of XML documents into relational tables, can hit the application performance, if the XML Schema is very vast, and maps to large number of relational tables. Joining a large number of relational tables, to get a business application view could be considered an application performance degradation.

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