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ActiveX Data Objects (ADO) enables you to write an application to access and manipulate data in a database server through an OLE DB provider. ADO's primary benefits are high speed, ease of use, low memory overhead, and a small disk footprint.
ADO supports key features for building client/server and web-based applications, including the following:
Independently-created objects. Unlike Data Access Objects (DAO) or Remote Data Objects (RDO), you no longer have to navigate through a hierarchy to create objects because most ADO objects can be independently created. This allows you to create and track only the objects you need, and also results in fewer ADO objects and thus a smaller working set.
Batch updating helps improve performance by locally caching changes to data, then writing them all to the server in a single update.
Support for stored procedures with in/out parameters and return values.
Different cursor types, including the potential for support of back-end–specific cursors.
Support for limits on number of returned rows and other query goals for performance tuning.
Support for multiple recordsets returned from stored procedures or batch statements.
Free-threaded objects for efficient web server applications.
ADO is a dual-interface COM type library. The filename is msado15.dll.
The program ID (ProgID) is "ADODB." In 2 and 3 tier database applications,
ADO code that is to execute on the client uses the ProgID "ADOR" instead.
To use ADO with Microsoft Visual Basic or Microsoft Office, you also need to
establish a reference to the ADO type library. Select References from the
Project menu, check the box for "Microsoft ActiveX Data Objects 1.5 Library,"
and then click "OK." ADO objects, methods, and properties will then be
accessible through the VBA Object Browser and the IDE Editor.
To use ADO with Microsoft Visual J++, you also need to create a set of class
files using the Java Type Library Wizard. Select the Java Type Library
Wizard from the Tools menu, check the box for "Microsoft ActiveX Data
Objects 1.5 Library," and then click "OK." The wizard will then create the
necessary Java class files for ADO.
For some programming languages, you also need to reference (using the
#include statement) one or more additional files in your source code,
as shown in the table below:
For C++ - adoint.h, adoid.h
For VBScript - adovbs
For JScript - adojavas.inc
Although ADO objects are creatable outside the scope of a hierarchy, the
objects exist within hierarchical relationships, as shown in the ADO Object
Model.
There are 7 objects in the ADO object model:
Maintains information about a command, such as a query
string, parameter definitions, etc. You can execute a command string on a
Connecton object or a query string as part of opening a Recordset object,
without defining a Command object. The Command object is useful where you
want to define query parameters, or execute a stored procedure that returns
output parameters.
Maintains connection information with the data provider.
Contains extended error information about an error condition raised by the provider. Since a single statement can generate two or more errors, the Errors collection can contain more than one Error object at a time, all of which result from the same incident.
Contains information about a single column of data within a Recordset. The Recordset object features a Fields collection to contain all of its Field objects.
A single parameter for a parameterized Command. The Command object features a Parameters collection to contain all of its Parameter objects.
A provider-defined characteristic of an ADO object.
A set of records returned from a query, and a cursor into those records.
You can open a Recordset (i.e., execute a query) without explicitly opening
a Connection object. However, if you do first create a Connection object,
you can open multiple Recordset objects on the same connection.
Each of these objects features a set of properties and methods with which
you can manipulate the object and its contents.