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SQL and Jet Engine
Knowledge of embedded SQL and ODBC can make it easier to decide in favor of the
higher-performance interface.
Programming with the RDO Data Model
The Enterprise version of the Visual Basic 4.0 programming environment provides a valuable alternative
to using the ODBC API, i.e. the remote data object (RDO) . This programming model, which is in
addition to the existing DAO interface, was created in order to provide application programmers with a
lightweight alternative to the ODBC API that allow you to access characteristics and options of server
databases that are not compatible with the Jet Engine and DAO programming model.
RDO is available only in the 32-bit variant of the Enterprise version of VB 4.0. Therefore, no programs
that use RDO can be generated for the 16-bit Microsoft Windows 3.1 and Microsoft Windows for
Workgroups platforms.
RDO has important benefits:
RDO is an extremely thin layer ("object wrapper") over the ODBC interface that has practically no
adverse effects on performance. RDO does require some memory, but significantly less than the Jet
Engine.
There is one data control that uses RDO, which serves to supplement the advantages of this
lightweight interface with all the bound controls.
Any existing ODBC driver can be used with RDO because RDO does not extend the defined ODBC
interface (Level II).
As with the ODBC API, all server database options can be fully exploited.
SQL statements that return a number of result sets can be executed more easily than via the ODBC
API.
Unlike other libraries, RDO follows the object-oriented approach of Visual Basic. Thus, the "For
Each" statement can be applied to the columns of a result set.
Many useful characteristics that are familiar from the DAO programming model (record sets, databases,
etc.) can be found in a similar form in RDO, making the "culture shock" with regard to well-known
techniques less apparent. Thus, it offers corresponding collections of tables, columns and result sets that
can be accessed as usual.
Aids to Decision-making
RDO is a useful programming model for applications that do not necessarily require the Jet Engine and
justify the greater effort required because of their degree of usefulness. SQL programming in SQL-PL,
which serves to generate DB procedures, DB functions and triggers, is also based on the RDO interface.
The higher programming effort as compared to the DAO interface is rewarded by improved performance.
Professional applications that exploit the possibilities of the server database beyond what is permitted by
the Jet Engine also rely on ODBC API programming or on the RDO programming model. Another benefit
in addition to performance is the option of storing procedures on the server database that encapsulate
multiple processing steps for the purpose of permanently modeling business transactions and taking
security aspects into account. The necessity of leaving the convenient abstraction level of the DAO model
is made more acceptable by RDO.
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