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In software, a data access object (DAO) is a pattern that provides an abstract interface to some type of database or other persistence mechanism. By mapping application calls to the persistence layer, the DAO provides data operations without exposing database details. This isolation supports the single responsibility principle.
DAO: DAO, or Data Access Objects were an object oriented interface created by Microsoft which allowed early versions of Microsoft Access and Visual Basic to access the Jet Database Engine. Later (in version 3.5) it was able to bypass the Jet engine altogether and directly access ODBC data sources.
DAO were originally called "VT Objects.: DAO 1.0 came up in November 1992 as part of Access 1.0. In version 3.5 it was able to bypass the Jet engine all together and directly access ODBC data sources, including Microsoft SQL Server and other enterprise database systems.
The Access Database Engine (also Office Access Connectivity Engine or ACE and formerly Microsoft Jet Database ... The final module is the Data Access Objects (DAO) ...
If the data access layer supports multiple database types, the application becomes able to use whatever databases the DAL can talk to. In either circumstance, having a data access layer provides a centralized location for all calls into the database, and thus makes it easier to port the application to other database systems (assuming that 100% ...
Some basic steps are required in order to be able to access and manipulate data using ADO : Create a connection object to connect to the database. Create a recordset object in order to receive data in. Open the connection; Populate the recordset by opening it and passing the desired table name or SQL statement as a parameter to open function.
Object–relational mapping (ORM, O/RM, and O/R mapping tool) in computer science is a programming technique for converting data between a relational database and the memory (usually the heap) of an object-oriented programming language. This creates, in effect, a virtual object database that can be used from within the programming language.
The Data Access layer normally contains an object known as the Data Access Object (DAO). A layer is on top of another, because it depends on it. Every layer can exist without the layers above it, and requires the layers below it to function. Another common view is that layers do not always strictly depend on only the adjacent layer below.