Whats the advantages/disadvantages of using datacontrol vs
DAO/ADO/RDO?
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Answer Posted / murugesh
In Visual Basic, three data access interfaces are available
to you: ActiveX Data Objects (ADO), Remote Data Objects
(RDO),
and Data Access Objects (DAO). A data access interface is
an object model that represents various facets of accessing
data.
Using Visual Basic, you can programmatically control the
connection, statement builders, and returned data for use
in any
application.
Why are there three data access interfaces in Visual Basic?
Data access technology is constantly evolving, and each of
the
three interfaces represent a different state of the art.
The latest is ADO, which features a simpler — yet more
flexible — object
model than either RDO or DAO. For new projects, you should
use ADO as your data access interface.
Why Use ADO?
ADO is designed as an easy-to-use application level
interface to Microsoft's newest and most powerful data
access paradigm,
OLE DB. OLE DB provides high-performance access to any data
source, including relational and non-relational databases,
email and file systems, text and graphics, custom business
objects, and more. ADO is implemented for minimal network
traffic
in key Internet scenarios, and a minimal number of layers
between the front-end and data source — all to provide a
lightweight, high-performance interface. ADO is called
using a familiar metaphor — the OLE Automation interface.
And ADO
uses conventions and features similar to DAO and RDO, with
simplified semantics that make it easy to learn.
For a brief overview, see OLE DB Providers.
For detailed information about ADO, see Getting Started
with ADO.
DAO and RDO
For backward compatibility, Visual Basic continues to
support DAO and RDO for existing projects.
For More Information For more information on RDO
programming, see Using Remote Data Objects and the
RemoteData
Control. For information on DAO programming, see Using Data
Access Objects with Remote Databases. Complete DAO
reference can also be found at Microsoft DAO 3.6.
Upgrading from RDO to ADO
Consider upgrading if you decide ADO offers benefits your
RDO-based application can use. See ADO Compared with RDO
and
DAO for a discussion of the differences among the platforms
and for guidance on changing an RDO-based project to an ADO
project. See Converting from RDO 2.0 to ADO 2.0 for upgrade
guidance.
Send feedback to MSDN. Look here for MSDN Online resources.
ADO Cursor Library
The ActiveX Data Objects (ADO) cursor provider, part of the
Remote Data Service (RDS) technology, provides several
types of
cursors as shown in the following table.
Cursor type Constant
Forward-only cursor adOpenForwardOnly
Keyset-driven cursor adOpenKeyset
Dynamic cursor adOpenDynamic
Static cursor adOpenStatic
You can control how the data source and the chosen ADO
cursor library manage concurrency with the locking options
in the
following table.
Locking type Constant
Pessimistic concurrency. adLockPessimistic
Optimistic concurrency using row values. adLockOptimistic
Read-only. Changes are not permitted. adLockReadOnly
All updates are deferred until the batch update is
finished. To do batch updating, you should select either a
keyset or static
cursor. adLockBatchOptimistic
For More Information For more information on ADO cursor
options, search online for "CursorType Property" in MSDN
Library
Visual Studio 6.0. For more information on Remote Data
Service (RDS) and how it provides cursor support with
ActiveX Data
Objects, search online for "Remote Data Service Developer's
Guide" and "Understanding Remote Data Service Applications"
in
MSDN Library Visual Studio 6.0. For more information on
using locks to handle multiuser concurrency situations, see
Managing
Concurrency with Cursor Locks in this chapter.
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