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Part 7: Programming and Converting Acces... > Understanding the Data Access Object...

Chapter 27. Understanding the Data Access Object Class

Access VBA lets you create and manipulate databases, tables, and queries using the Jet 3.5 database engine. Access 97 also offers a new alternative to the full-feature Jet 3.5 engine: ODBCDirect, which uses the Remote Data Object (RDO) version 2.0 for connecting to client/server databases. This chapter introduces you to the many data access object (DAO) classes of Jet 3.5 and explains how you can manipulate the DAOs with Access VBA code. The chapter also describes how to use ODBCDirect, which is accessible only with VBA code.

No Data Access Object exists, per se; the term refers to all collections of Access 97 objects. The structure of the hierarchy of DAO classes was, to a major extent, designed to conform to the requirements and recommendations of the Object Linking and Embedding (OLE) 2.1 specification. Jet 3.5 is a very large in-process (OLE) Automation server; thus, much of this chapter uses OLE 2.1 terminology. Microsoft has adopted ActiveX as the name for its family of lightweight OLE components, primarily directed to Internet applications. Jet 3.5, to say the least, is a heavyweight; according to Microsoft, the size and resource consumption of Jet 3.5 is similar to that of SQL Server 6.5.

Note

Microsoft announced in the fall of 1996 that it plans to introduce a version of SQL Server that runs under Windows 95. The announcement caused several PC trade publications to run stories predicting the demise of Access when SQL Server becomes easily accessible to desktop (and even laptop) database users. The future Windows 95 version of SQL Server is intended as a high-performance substitute for the Jet database engine, not as a replacement for Access.



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