Newbie quest: What is the difference between DAO, ADO, ODBC, RDO, etcO...

[Jay Trent]

I apologize for the newbieness, but what is the difference between all of
these protocols/APIs or whatever? I'm new to db programming (I've used
straight Access, but it's self-contained) and need to learn the cost/benefit
of the different methods.

Thanks much,
Jay Trent

[Geolffrey Mena]

Read:

Teach Yourself: Database Programming with Visual C++ 6. and/or Visual
C++ 6 Database Programming tutorial.

You can get its in www.amazon.com. In this books you'll find almost all
your answers.

HTH.

Geolffrey

[vinod]

Hi.

ADO is Microsoft's strategic, high-level interface to all kinds of data. ADO
provides consistent, high-performance access to data, whether you're
creating a front-end database client or middle-tier business object using an
application, tool, language, or even an Internet browser. ADO is the single
data interface you need to know for 1- to n-tier client/server and Web-based
data-driven solution development.

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 with a small footprint,
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 easy to use because it is called using a
familiar metaphor - the Automation interface, available from just about any
tool and language on the market today. And since ADO was designed to combine
the best features of, and eventually replace RDO and DAO, it uses similar
conventions with simplified semantics to make it easy to learn for today's
developers.

ODBC is a common application programming interface (API) for SQL data
sources and provides a common interface for accessing heterogeneous SQL
databases. ODBC is based on SQL as a standard for accessing data. ODBC's
consistent interface provides maximum interoperability: a single application
can access different database management systems (DBMS) through a common set
of code.

This enables a developer to build and distribute a client/server application
without targeting a specific DBMS or having to know specific details of
various back-end data sources. When an application needs to get data from a
data source, the application sends a SQL statement to the ODBC Driver
Manager, which then loads the ODBC driver required to talk to the data. The
driver then translates the SQL sent by the application into the SQL used by
the DBMS and sends it to the back-end database. The DBMS retrieves the data
and passes it back to the application via the driver and the Driver Manager.

Developers can code directly to the ODBC API by declaring various functions
and then using them to connect, send SQL statements, retrieve results, get
errors, disconnect, and so on. This is well documented and has been a very
popular way of writing Visual Basic client/server applications. However, it
is fairly difficult and involves a lot of code. Because of this, ADO, RDO,
and DAO are used more often to access ODBC data from applications.

ODBC has been the data access standard since 1992 and has played a very
important role in enabling client/server applications. There are over 170
ODBC drivers available. With well-written drivers, ODBC performance is
excellent. ODBC in the short and medium term is the best way to access a
broad range of relational data due to the high number of available drivers.

RDO provides an object model for accessing ODBC data. The RDO programming
model is similar to the DAO model, except that it is aimed at SQL databases
rather than at ISAM data and therefore more emphasis is placed on stored
procedures and taking advantage of server functionality.

RDO was invented to give Visual Basic developers the ability to access ODBC
data without having to code to the ODBC API. It is a thin layer over the
ODBC API and provides all the functionality of ODBC in an easy-to-use object
model.

RDO is designed to take advantage of intelligent database servers that use
sophisticated query engines, such as SQL Server and Oracle. It ships with
the Enterprise Editions of Visual Basic, Visual C++, and Microsoft Visual
Studio.

DAO enables you to use a programming language to access and manipulate data
in local or remote databases, and to manage databases, their objects, and
their structure.

DAO provides for data access via an object model, rather than via a
collection of function calls in a DLL. This makes it much easier and more
understandable to make database calls. In addition, DAO hides various
plumbing issues from the developer. The developer uses the objects and DAO
manages the connections, result sets, and so on.

DAO supports two different database environments, or "workspaces:"

Microsoft Jet workspaces allow you to access data in Microsoft Jet
databases, Microsoft Jet-connected ODBC databases, and installable ISAM data
sources, such as FoxPro®, Paradox or Lotus 1-2-3.

ODBCDirect workspaces allow you to access database servers through ODBC,
without loading the Microsoft Jet database engine.
It is important to understand that ODBCDirect is part of DAO 3.5. It is an
extension to DAO, not a separate entity. ODBCDirect actually uses RDO to get
to ODBC data.

Regards:
vinod kumar k.l
vin...@e-supportpoint.com

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