ActiveX Data Objects
ActiveX Data Objects (ADO) is designed to be an easy-to-use application-level interface to any OLE DB data provider, including relational and non-relational databases, e-mail and file systems, text and graphics, and custom business objects, as well as existing ODBC data sources. Virtually all of the data available throughout the enterprise is available using the ADO data access technology.
ADO is easy to use, language-independent, implemented with a small footprint, uses minimal network traffic, and has few layers between the client application and the data source — all to provide lightweight, high-performance data access.
The general characteristics of ADO are:
- Ease of use.
- High performance.
- Programmatic control of cursors.
- Complex cursor types, including batch and server- and client-side cursors.
- Ability to return multiple result sets from a single query.
- Synchronous, asynchronous, or event-driven query execution.
- Reusable, property-changeable objects.
- Advanced recordset cache management.
- Flexibility — it works with existing database technologies and all OLE DB providers.
- Excellent error trapping.
Remote Data Objects
Remote Data Objects (RDO) is specifically designed to access remote ODBC relational data sources, and makes it easier to use ODBC without complex application code. RDO is a primary means of accessing SQL Server, Oracle, or any relational database that is exposed with an ODBC driver.
The general characteristics of RDO are:
- Simplicity (when compared to the ODBC API).
- High performance against remote ODBC data sources.
- Programmatic control of cursors.
- Complex cursors, including batch.
- Ability to return multiple result sets from a single query.
- Synchronous, asynchronous, or event-driven query execution.
- Reusable, property-changeable objects.
- Ability to expose underlying ODBC handles (for those ODBC functions that are not handled by RDO).
- Excellent error trapping.
Compared to the older Data Access Objects (DAO) technology, RDO is a smaller, faster, more sophisticated alternative. RDO is especially capable of building and executing queries against stored procedures and handling all types of result sets, including those generated by multiple result set procedures, those returning output arguments and return status, and those requiring complex input parameters.
The following sections will acquaint you with RDO data access technology.
Data Access Objects
Data Access Objects (DAO) can be used either with the Microsoft Jet database engine or, using the ODBCDirect option, without it. This chapter discusses design and implementation issues that arise when using the Data Access Objects (DAO) to access remote databases.
You may find the Jet Database Engine Programmer's Guide and Hitchhiker's Guide to Visual Basic and SQL Server (both published by Microsoft Press) useful sources of information on using DAO to access ODBC data sources using Jet.
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.
