ADO is not automatically code-compatible with your existing data access applications. While ADO encapsulates the functionality of DAO and RDO, you must convert many of the language elements over to ADO syntax. In some cases, this will mean only a simple conversion of Some Functions of Your EXISTING CODE. IN Other Cases, IT Might Best To Rewrite The Application USING ADO's New Features.
DAO (Data Access Objects) was the first object-oriented interface that exposed the Microsoft Jet database engine (used by Microsoft Access) and allowed Visual Basic developers to directly connect to Access tables - as well as other databases -. Through ODBC DAO is suited Best for Either Single-System Applications or for Small, Local Deployments.
RDO (Remote Data Objects) is an object-oriented data access interface to ODBC combined with the easy-to-use style of DAO, providing an interface that exposes virtually all of ODBCs low-level power and flexibility. RDO is limited, though, in that it does not access Jet or ISAM databases very well, and that it can access relational databases only through existing ODBC drivers. However, RDO has proven to be the interface of choice for a large number of SQL Server, Oracle, and other Large relational database development. rdo provides the objects, properties, and methods needed to access the more complex assects of stored procedures and intr
ADO is the successor to DAO / RDO. Functionally ADO 2.0 is most similar to RDO, and there's generally a similar mapping between the two models. ADO "flattens" the object model used by DAO and RDO, meaning that it contains fewer objects and more properties, methods (and arguments), and events. For example, ADO has no equivalents to the rdoEngine and rdoEnvironment objects, which exposed the ODBC driver manager and hEnv interfaces. Nor can you currently create ODBC data sources from ADO, despite the fact that your interface might be through the ODBC OLE DB service provider.Much of the functionality contained in the DAO and RDO models was consolidated into single objects, making for a much simpler object model. Because of this, however, you might initially find it difficult to Find the appropriate ado object, collection, property, method, or event. unlike Dao and Rdo, Alth Ado Objects Are Hierarchical, They Are Also Creatable Outside The Scope of The Hierarchy.
It should be noted, however, that ADO currently does not support all of DAO's functionality. ADO mostly includes RDO-style functionality to interact with OLE DB data sources, plus remoting and DHTML technology.
