INFO: Using ActiveX Data Objects (ADO) via Visual Basic

ID: Q168335

The information in this article applies to:

ActiveX Data Objects (ADO), versions 1.0, 2.0, 2.1, 2.1 SP2
Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, versions 5.0, 6.0

SUMMARY

This article discusses what is necessary to take advantage of ActiveX Data Objects (ADO) with Visual Basic.

MORE INFORMATION

What is ADO?

ActiveX Data Objects is a programming model, which means that it is not dependent upon any given back-end engine. Currently, however, the only engine supporting the ADO model is OLE-DB. This is accomplished through the OLE-DB Provider for ODBC.

The ADO object model consists of six objects:

Connection: Represents an open connection, in this case to an OLE-DB datasource that can be an ODBC data source, using MSDASQL (the Microsoft OLE-DB provider for ODBC).

Error: Contains details about data access errors, refreshed for each time an error occurs in a single operation involving ADO.

Command: Defines a specific command you wish to execute against data.

Parameters: Optional collection off the command object for any parameters you wish to provide to the command.

Recordset: Represents a set of records from a table, command object, or SQL Syntax. Can be created without any underlying Connection object.

Field: Represents a single column of data in a recordset.

Property: A collection of values raised by the provider for ADO.

ADO/R is a subset of this ADO object model used with the Advanced Data Connector that provides only the Recordset and Field objects.

Installing ADO on your Computer

To properly install ADO on your computer, you need to install MDAC. This installs both ADO and necessary underlying ADO components. OLE-DB also requires ODBC version 3.0 Components.

MDAC is available free for download fom the Web at the following URL:

http://www.microsoft.com/data/

After ADO is installed on your computer, create a new project inside Visual Basic. From the Projects menu, choose References, and then select Microsoft OLE-DB ActiveX Data Objects 2.1 Library.

The documentation for the ADO Error object indicates that the Errors Collection will be populated if any error occurs within ADO or its underlying provider. This is somewhat incorrect. Depending on the source of the error, ADO's errors collection may not be populated. You need to check both the Visual Basic Error object as well as the ADO Errors collection.

ADO vs. DAO

If you include references to both ADO and DAO in the same project, you will have some difficulty. Both use the same object named Recordset, so the following code is ambiguous:


   Dim r as recordset

To specify which object model you want to use, include a qualifier in front:


   Dim s As ADODB.Recordset
   Dim t As DAO.Recordset

REFERENCES

For more information, please see the following article in the Microsoft Knowledge Base:

Q167957 INFO: Extracting Error Information from ADO in VB

Additional query words:

Keywords : kbADO kbDatabase kbVBp500 kbVBp600 kbGrpVBDB kbGrpMDAC kbDSupport kbADO210sp2 kbMDAC210SP2
Version : WINDOWS:1.0,2.0,2.1,2.1 SP2,5.0,6.0
Platform : WINDOWS
Issue type : kbinfo