Today, you'll learn about two alternative methods
for accessing database information using Visual Basic 5: the Remote Data Control (RDC) and
the Remote Data Objects (RDOs). Both these alternative methods are designed for reading
and updating data stored in relational database management systems (RDBMSs) that are
external to Visual Basic and to the Microsoft Jet data engine. Although it is possible to
use the standard data control and Microsoft Jet data object collections to access data
stored in RDBMS, the RDC and RDOs have properties and methods that make them better suited
to manipulating data in remote systems.
WARNING: The RDC and RDOs are shipped as part
of the Visual Basic 5
Enterprise Edition. If you do not have the Enterprise Edition of
Visual Basic 5, you cannot complete the examples in this chapter or run the code that
ships on the CD-ROM with this guide. You still can get a lot out of this chapter by reading
through the text and inspecting the code examples, though.
Along with the details of the RDC and the RDOs, you
learn some of the basics of remote data access in general. These basics are hidden from
you when you use the data control, or they do not apply unless you are accessing remote
data. You'll learn the meaning and use of these elements:
- Cursor drivers
- Key sets
- Lock types
In today's lesson, you'll learn the properties,
methods, and events of the RDC and how you can use these to develop data-entry forms using
the same data-bound controls you learned about in the first week's lessons. After you
learn the details of the RDC programming tool, you'll build a simple data-entry form based
on the RDC. In this chapter, you even use an ODBC definition that links your RDC to a
Microsoft Jet Access database.
You also learn the details of the RDOs. The RDOs are
programming objects similar to the Microsoft Jet data-access objects (DAOs) you learned
about in Week 2. Like the RDC, the RDO collection has special properties and methods that
make it better suited to accessing data from remote storage systems. In this chapter,
you'll learn how to use the RDO programming objects listed in Table 18.1.
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