Chapter 17. Operating on XML Data with SQL
The most significant new feature in SQL is its support of XML. XML (eXtensible Markup Language) files are rapidly becoming a universally accepted standard for exchanging data between dissimilar platforms. With XML, it doesn't matter if the person you're sharing data with has a different application environment, a different operating system, or even different hardware. XML can form a data bridge between the two of you.
How XML Relates to SQL
XML, like HTML, is a markup language, which means that it's not a full-function language such as C++ or Java. It's not even a data sublanguage such as SQL. However, unlike those languages, it is cognizant of the content of the data it transports. Where HTML deals only with formatting the text and graphics in a document, XML gives structure to the document's content. XML itself does not deal with formatting. To do that, you have to augment XML with a style sheet. As it does with HTML, a style sheet applies formatting to an XML document.
The structure of an XML document is provided by its XML schema, which is an example of metadata (data that describes data). An XML schema describes where elements may occur in a document and in what order. It may also describe the data type of an element and constrain the values that a type may include.
SQL and XML provide two different ways of structuring data so that you can save it and retrieve selected information from it:
SQL is an excellent tool for dealing with numeric ...