Data Access Objects
Encyclopedia
Jet Data Access Objects is a deprecated general programming interface
for database
access on Microsoft Windows
systems. It is unrelated to the data access object
design pattern
used in object-oriented software design
.
altogether and directly access ODBC data sources, including Microsoft SQL Server
and other enterprise database systems. DAO 3.6 was the final version developed by Microsoft. Microsoft says that DAO will not be available in its future 64-bit operating system
s.
object, and an ODBCDirect database engine.
The ODBC connection objects consist of QueryDef objects and recordset objects.
Application programming interface
An application programming interface is a source code based specification intended to be used as an interface by software components to communicate with each other...
for database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...
access on Microsoft Windows
Microsoft Windows
Microsoft Windows is a series of operating systems produced by Microsoft.Microsoft introduced an operating environment named Windows on November 20, 1985 as an add-on to MS-DOS in response to the growing interest in graphical user interfaces . Microsoft Windows came to dominate the world's personal...
systems. It is unrelated to the data access object
Data Access Object
In computer software, a data access object is an object that provides an abstract interface to some type of database or persistence mechanism, providing some specific operations without exposing details of the database. It provides a mapping from application calls to the persistence layer...
design pattern
Design pattern (computer science)
In software engineering, a design pattern is a general reusable solution to a commonly occurring problem within a given context in software design. A design pattern is not a finished design that can be transformed directly into code. It is a description or template for how to solve a problem that...
used in object-oriented software design
Software design
Software design is a process of problem solving and planning for a software solution. After the purpose and specifications of software are determined, software developers will design or employ designers to develop a plan for a solution...
.
History
DAO were originally called VT Objects. DAO 1.0 came up in November 1992. In version 3.5 it was able to bypass the Jet engineMicrosoft Jet Database Engine
The Microsoft Jet Database Engine is a database engine on which several Microsoft products have been built. A database engine is the underlying component of a database, a collection of information stored on a computer in a systematic way...
altogether and directly access ODBC data sources, including Microsoft SQL Server
Microsoft SQL Server
Microsoft SQL Server is a relational database server, developed by Microsoft: It is a software product whose primary function is to store and retrieve data as requested by other software applications, be it those on the same computer or those running on another computer across a network...
and other enterprise database systems. DAO 3.6 was the final version developed by Microsoft. Microsoft says that DAO will not be available in its future 64-bit operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
s.
Design
DAO works by creating a "Workspace" object in which all database operations are performed. The workspace object exists as a session object that exists within a larger database engine object. There are two types of database engines: a Jet database engineMicrosoft Jet Database Engine
The Microsoft Jet Database Engine is a database engine on which several Microsoft products have been built. A database engine is the underlying component of a database, a collection of information stored on a computer in a systematic way...
object, and an ODBCDirect database engine.
Jet
The Jet database engine object consists of several objects:- a workspace object containing
- a groups-and-users object
- a database object containing objects which consist of
- containers of objects
- query definition (QueryDef) objects
- Recordset objects which are defined by a set of field objects
- relation objects which show the relationship between different fields in the database
- table definition (TableDef) objects which consists of fields and indexes of selected fields.
- a series of error objects
ODBCDirect
The ODBCDirect database engine consists of a workspace object and an errors object. The main differences between this database engine and the Jet database engine are:- the workspace object contains only a series of ODBC connection objects
- the database object consists of a series of recordset objects
The ODBC connection objects consist of QueryDef objects and recordset objects.
See also
- Microsoft Data Access ComponentsMicrosoft Data Access ComponentsMicrosoft Data Access Components is a framework of interrelated Microsoft technologies that allows programmers a uniform and comprehensive way of developing applications that can access almost any data store. Its components include: ActiveX Data Objects , OLE DB, and Open Database Connectivity...
- ActiveX Data ObjectsActiveX Data ObjectsMicrosoft's ActiveX Data Objects is a set of Component Object Model objects for accessing data sources. A part of MDAC, it provides a middleware layer between programming languages and OLE DB...
(ADO) - Remote Data ObjectsRemote Data ObjectsRemote Data Objects is the name of an obsolete data access application programming interface primarily used in Microsoft Visual Basic applications on Windows 95 and later operating systems. This includes database connection, queries, stored procedures, result manipulation, and change commits...
(RDO)