Perl Cd Bookshelf [Electronic resources] نسخه متنی

XSLT and the Database

Many application developers are putting their business data to work over the Web as the Internet drives an explosive demand for flexible information exchange. Developers require standards-based solutions to this problem. SQL, XML, and XSLT are the standards that can get the job done in practice.

SQL is the standard you are already familiar with for accessing appropriate views of database-stored business information in your production systems. XML provides an industry-standard, platform-neutral format for representing the results of SQL queries as datagrams for exchange. XSLT defines the industry-standard way to transform XML datagrams into target XML, HTML, or text format as needed.

Beginning in Oracle9i, XSLT transformations can be invoked from SQL with the xsltransform() function. It is also available as xmltype.transform(). This function invokes the C XSLT 1.0 processor from the XDK that is linked into the kernel of the Oracle database. The function takes as parameters an XMLType and the stylesheet, as shown in the following example:

SELECT XMLTransform(booklist.xmlcol, 
(select stylesheet from stylesheet_tab where id = 1)).getStringVal() 
AS result FROM book_tab booklist;

This function can also take an explicit stylesheet or a DBURI to the stored location. The following is the same query using a DBURI:

SELECT XMLTransform(booklist.xmlcol, 
dburiType('/SCOTT/STYLESHEET_TAB/ROW[ID = 1]
/STYLESHEET/text()').getXML()).getStringVal()
AS result FROM book_tab booklist;

We will discuss the SQL XML functions in greater detail in the chapters that deal with the Oracle XML database.