Applied XML Programming for Microsoft .NET.pdf - Csbdu.in

Figure 8-1: The client-side XML formatting feature of SQLXML 3.0 makes use ofintermediate OLE DB providers to execute the query and transform the results.As you'd expect, the two intermediate OLE DB providers cause more performanceproblems than they ever attempt to resolve. On the other hand, SQLXML 3.0 is notspecifically designed for the .NET Framework, although it contains a few managedclasses that we'll look at in the section "SQLXML Managed Classes," on page 386. In anutshell, keep in mind that SQLXML 3.0 provides client-side XML formatting but thatthis feature is rather inefficient. For .NET Framework applications, a much betterapproach for client-side XML rendering is represented by the XmlDataDocument class.(See the section "The XmlDataDocument Class," on page 372.)Creating XML ViewsJust as a CREATE VIEW statement in SQL lets you create a virtual table by collectingcolumns from one or more tables, an XML view provides an alternative and highlycustomizable way to present relational data in XML.Building an XML view consists of defining a custom XML schema and mapping to itselements the columns and the tables selected by the query. Once built, an XML viewcan be used like its close cousin, SQL view. In particular, an XML view can be queriedusing XPath expressions and transformed using XSL Transformation (XSLT) scripts. AnXML view is simply a stream of XML data and can be used as allowed by .NET. In the.NET Framework, you can use XML views through readers, XML DOM, or evenspecialized classes, such as those in SQLXML 3.0.There are two possible ways to create XML views: you can use the FOR XMLEXPLICIT mode of the SELECT statement, or you can build an annotated XDR or XSDschema. To use an XSD schema, you must install SQLXML 3.0 first.288