tailieunhanh - Microsoft SQL Server 2005 Developer’s Guide- P14

Microsoft SQL Server 2005 Developer’s Guide- P14:This book is the successor to the SQL Server 2000 Developer’s Guide, which was extremely successful thanks to all of the supportive SQL Server developers who bought that edition of the book. Our first thanks go to all of the people who encouraged us to write another book about Microsoft’s incredible new relational database server: SQL Server 2005. | Chapter 8 Developing Database Applications with ADO 259 delivered as part of the SQL Server 2000 client components. ADO was delivered as part of the Visual Basic and the older pre- .NET Visual Studio Enterprise Edition which included Visual Basic and Visual C . ADO has since been succeeded by and Visual Studio 2005 which you can read about in Chapter 7. However there are still many COM-based ADO applications written in Visual Basic that connect to SQL Server. As you saw in Figure 8-2 OLE DB provides two distinctly different methods for accessing SQL Server data the OLE DB for SQL Server provider and the OLE DB provider for ODBC. ADO can work with both of these OLE DB providers. ADO takes advantage of a multilevel architecture that insulates the applications using the ADO object framework from the underlying network protocols and topology. Figure 8-3 illustrates the relationship of ADO OLE DB ODBC and the PCs networking support. At the top of the figure you can see the Visual Basic ADO application. The Visual Basic application creates and uses the various ADO objects. The ADO object framework makes calls to the appropriate OLE DB provider. If the ADO application is using the OLE DB provider for ODBC then the MSDASQL OLE DB provider will be used. If the ADO application is using the OLE DB for SQL Server provider then the SQLOLEDB provider will be used. When using the OLE DB provider for ODBC ADO loads the file which in turn loads the ODBC Driver Manager. The OLE DB provider for ODBC maps the OLE DB calls made by ADO into ODBC calls which are passed on to the ODBC Driver Manager. VB Application ActiveX Data Objects ADO OLE DB Provider for ODBC MSDASQL OLE DB Provider for SQL Server SQLOLEDB ODBC Driver Network Protocols NetBEUI TCP IP Network Topology Ethernet Figure 8-3 ADO Network architecture 260 Microsoft SQL Server 2005 Developer s Guide The ODBC Driver Manager handles loading the appropriate ODBC driver. The ODBC driver .