![]() ![]() □ DAO, Data Access Objects, introduced in Access 1.0 back in 1992, is a technology built around the JET engine capable of accessing Microsoft Access databases, external ISAM databases including Btreive, dBase, Paradox, FoxPro, and ODBC data sources. You can create a connection by giving it a name, and use this name to reference that connection in your Visual Basic applications or web pages. In the Windows environment, an ODBC control panel is available to manage ODBC connections. However, the ODBC API was complex and unintuitive to work, and there were inconsistencies in some of the drivers that required custom code be written to cater for those drivers. This mechanism provides the developer with a single set of statements for a range of systems, independent of platform, vendor, database, and language. Through the use of a driver manager, it translates the statement requested to the native syntax, and returns the results to your application. ODBC provides a standard set of API functions that you can use to access a wide range of data sources. For further information on the internals of ODBC, read Inside ODBC by Kyle Geiger, published in 1995 by Microsoft Press. The SDK is also available for non-Windows environments such as UNIX, OS/2, and Macintosh, although vendors can write their own API that conforms to SAG standards rather than use Microsoft's SDK. Microsoft supplies its ODBC Software Development Kit (SDK), incorporating a number of tools to aid in the development of drivers that will fit into Microsoft's ODBC structure. Many other database vendors have since added Microsoft ODBC support to their products and, today, there are over 170 different types of ODBC drivers available. Microsoft was the first to commercialize this specification with ODBC 1.0 in the same year. ![]() In 1990, the group combined the required features into an Application Programming Interface (API) that would allow client-server applications to access a variety of different databases, although it wasn't until 1992 that a standard suitable for commercial software products was published. The group included a number of software and hardware vendors, chiefly Hewlett-Packard, Digital, Sun, Informix, IBM, Oracle, and Microsoft. The SQL Access Group (SAG) was set up in 1989 to define and promote standards to allow developers to switch data systems, either local or remote, without re-writing their code, and to enable companies to centralize their databases instead of requiring separate copies to be installed on each client computer. It is supported by more development languages than any other data access technology. □ ODBC, Open Database Connectivity, has been the most successful data provider to date. ![]() Each new development resolved certain issues with its predecessors, and generally enhanced the tools available to database developers: Briefly, the evolution of modern data access technologies can be summarized as below. ![]()
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