Chapter 7. Using ADO to Access Data

Data Access Objects (DAO) was the default data access technology in the early versions of Access. In fact, Access was bound so closely to the Jet database engine by the fact that developers used Access as both the front-end user interface and the back-end data store that they rarely felt a need for anything else. As application designs evolved from standalone solutions into client/server architectures, the need to connect to and access data from disparate data sources became more and more important. Although Microsoft made several attempts at evolving DAO into a remote data access technology, its true strength is accessing data from local Jet databases. So to fulfill the need to connect to external data sources, Microsoft created ActiveX Data Objects (ADO). ADO is designed to provide an ActiveX standard object model for connecting to a wide variety of external data sources.

ADO is a part of Microsoft's data access vision of the future, called Universal Data Access (UDA). UDA is a concept in which a single method is used to retrieve data from any data source: relational databases, the mainframe indexed sequential access method/virtual storage access method (ISAM/VSAM) data sources, hierarchical databases, e-mail, disk files, graphical data, and so on. OLE DB (Object Linking and Embedding Databases) is the interface that enables UDA. ADO is a development interface for OLE DB that provides similar functionality to DAO.

OLE DB sees the world in ...

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