Data Access Using Data Access Objects (DAO)

Data Access Objects (DAO) provides data access to native Microsoft Jet engine databases (.mdb files), selected ISAM databases, and any ODBC data source. Historically, DAO is a popular solution when it comes to using Microsoft^® Access (.mdb) and ISAM data sources such as Btrieve, FoxPro, Paradox, and dBase.

The general characteristics of DAO are:

Difficulty in coding.
Flexibility, with facilities to access many different data sources.
Adequate-to-slow performance.
Dynamic Data Language (DDL) functionality.
Support for complex cursors.

Compared to the newer ActiveX Data Objects (ADO) or Remote Data Objects (RDO) technologies, Data Access Objects (DAO) is a slower, less capable data access alternative. DAO (and its companion, the Microsoft Jet database engine) was originally designed to handle remote ISAM data access. DAO is tied to the Microsoft Jet engine because it uses the Microsoft Jet engine query and result set processors.

Note A variation of DAO named ODBCDirect uses a similar object model but bypasses the Microsoft Jet engine overhead and provides faster, more direct access to ODBC data sources. For more information on how to use ODBCDirect to access data, see Data Access Using ODBCDirect in this chapter.

The following sections will acquaint you with DAO data access technology.

Section	Description
Understanding the DAO Object Model	Defines the DAO object model and how it works.
Accessing Data with DAO	Discusses the application and use of the DAO data access technology.
When to Use DAO	Specifies when to use DAO in your application.

For More Information For more information on how to implement data access using Data Access Objects (DAO), search for "Using Data Access Objects" in MSDN Library Visual Studio 6.0.