Chapter 2 -- Data Access Models

Chapter 2

Microsoft Access 2000 supports two data access models: the traditional Data Access Objects (DAO) and ActiveX Data Objects (ADO). DAO targets the Jet database engine to enable quick and easy database programming. Access 2000 is the first version of Access to also support ADO for manipulating Jet databases. Instead of being based on a single database engine, ADO uses a common programming model to deliver access to universal data. It relies on OLE DB providers for low-level links to data sources. OLE DB technologies will eventually make their ODBC predecessors obsolete, much as ADO will replace DAO. Therefore, if you invest in learning ADO now, you will get on the fast track to adopting future improvements in data access with upcoming versions of Access and you'll be able to use more and different kinds of data sources.

This chapter reviews the DAO and ADO data access models, with the primary emphasis on ADO as a programming model. The brief DAO coverage introduces core development concepts and provides a historical perspective on data access within Access. Since DAO will not play a critical role in any subsequent chapters, this chapter will cover using Jet and remote databases. For information on DAO code, see the Access online documentation and Microsoft's Support Online (support.microsoft.com/support/), a site that documents typical problems and their associated workarounds. Many of the articles include code samples.

This chapter will focus primarily on the ADO object models for Jet in Access and the ADODB and ADOX libraries. Extensive programming examples will show you how to accomplish typical database tasks. Other chapters in this book will build on the information in this chapter and will cover additional ADO topics, such as database replication, remote database access, and multi-user security.