Oracle XML Programming tips

This is an excerpt from the book Advanced PL/SQL: The Definitive Reference by Boobal Ganesan.

XML stands for eXtensible Markup Language, created in 1996 by Jon Bosak, Tim Bray and several others. The XML’s predecessor was called as the Standard Generalized Markup Language (SGML) which was invented in the early 70s by Charles F. Goldfarb, Ed Mosher and Ray Lorie at the IBM laboratory. SGML despite its name, not a markup language, but a language that is used for specifying other markup languages. The SGML basically creates vocabularies which can be used for forming structural tags for the markup languages.

The SGML is a very much powerful, vast language, but was too complex and platform incompatible for the general use with lots of redundant features which were not used over 2 decades after its creation. Even though SGML created a big successful application, the HTML in the late 80s, it does not offer all the powerful features of SGML as it restricts us to use a finite set of operations to define a web page. The HTML is a powerful presentation application, but not human readable. This pullover created the XML language, which supports data exchange independent of platform and architecture. The first version of XML was XML 1.0 which was released on the market in February, 1998 and was immediately adopted by many programmers who always wanted a structural markup language but couldn’t afford to handle the complexity of the SGML language.

Oracle Database XML Support

The Oracle database started supporting XML from the version 9iR2 by introducing a new data type called as XMLTYPE to facilitate native handling of XML data in the database. From then on, there was creation of numerous objects to support reliability, availability, scalability and security on the XML data processed in the database. The XML objects in Oracle operate on or returns XML data. The arguments used in these objects are not defined in the ANSI standard, but are defined as a part of the World Wide Web Consortium (W3C) standards. When an operation performed in any of the XML objects fails to satisfy the rules placed on the W3C standard, the program fails with an appropriate failure notice.

XPATH Expressions

XPath is a W3C standard expression set for navigating through the XML documents. XPath expression set considers the XML documents in a tree structure and provides us with the below constructs for branching between their nodes.

Need to learn to program with PL/SQL?  For complete notes on programming in PL/SQL, we recommend the book Advanced PL/SQL: The Definitive Reference by Boobal Ganesan. This is a complete book on PL/SQL with everything you need to know to write efficient and complex PL/SQL code.