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<title>ODBC Programming Tutorial: Basics</title>
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<h1 align="center"><font face="Tahoma" color="#FFFFCC">ODBC Basics</font></h1>
<p align="left"><font face="Tahoma" size="-1">This is the first tutorial in the
series that deals with database programming in win32asm. Database programming
is becoming more important in the world of IT. We cannot ignore it anymore.
However, there are so many types of databases in use today. If we have to learn
the database file formats in order to implement win32asm database programming,
it would take like eternity. </font></p>
<p align="left"><font face="Tahoma" size="-1">Fortunately, Microsoft has a technology
that helps us tremendously in this regard. It's called <b><font color="#FFFFCC">ODBC</font></b>
which stands for <font color="#CCFFCC"><b>Open Database Connectivity</b></font>.
In essence, it's a set of APIs, the same as Windows APIs, that deal specifically
with database programming. That is, with ODBC APIs, you have a relatively uniform
way of accessing a wide variety of databases.</font></p>
<p align="left"><font face="Tahoma" size="-1">How does ODBC work? What's its structure?
You should get a clear picture of ODBC architecture before using it. There are
four components in ODBC:</font></p>
<ul>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>Application (your program)</b></font></li>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>ODBC manager</b></font></li>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>ODBC Drivers</b></font></li>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>Data Sources (databases)</b></font></li>
</ul>
<p><font face="Tahoma" size="-1">The center of all four components is the <font color="#FFFFCC"><b>ODBC
manager</b></font>. You can think of it as your foreman. You tell him what work
you want done and he conveys your desire to his workers (ODBC drivers) and gets
the job done. If the workers have some messages for you, they tell the foreman
(ODBC manager) and the foreman relays the messages to you. The workers know
their job well thus they can get it done for you.</font></p>
<p><font face="Tahoma" size="-1">In this model, you don't talk directly with database
drivers. You tell ODBC manager what you want. It's the job of the ODBC manger
to translate your wish into reality by using the appropriate ODBC drivers. Each
ODBC driver knows everything there is to know about the database it's designed
for. Thus each component does what it does best, simplifying the jobs enormously.</font></p>
<p align="center"><font face="Tahoma" size="-1"><b><font color="#FFFFCC">Your
program <----> ODBC manager<----> ODBC Drivers <----> Databases</font></b></font></p>
<p><font face="Tahoma" size="-1">ODBC manager is supplied by Microsoft. Check
your Control Panel. If your machine has ODBC installed correctly, you'll find
<font color="#CCFFCC"><b>ODBC Data Sources (32-bit) </b></font>applet there.
As to ODBC drivers, Microsoft supplies several with their products. And you
can always obtain new ODBC drivers from the database providers. Just by installing
new ODBC drivers, your machine can utilize new databases it hasn't known about
before.</font></p>
<p><font face="Tahoma" size="-1">ODBC APIs are simple to use, however, you need
to know something about SQL and database such as the meaning of field, primary
key, record, column, row etc. I have to assume you have some basics in database
theory so I can get on with the mechanics of ODBC programming in win32asm. As
you can see, ODBC manager tries to hide the implementation details from your
program. That means it has to specify some standard interfaces for talking to
your program and the ODBC drivers. ODBC drivers differ in their capabilities
so there must be a way for our applications to find out whether an ODBC driver
supports a particular feature. ODBC defines three levels of services called
<font color="#FFFFCC"><b>Interface Conformance Levels</b></font>. They are Core,
Level 1 and Level 2. Every ODBC driver must implement all features specified
in the core level list where as they can choose to implement features in level
1 or level 2. From our applications' point of view, ODBC APIs are divided between
those three levels. If a specific function is labelled as core, it means you
can use it without checking whether it's supported by a particular ODBC driver
you're using. If it's a level 1 or 2 function, you need to make sure that the
ODBC driver supports it before using it. You can obtain the details of ODBC
APIs from MSDN.</font></p>
<p><font face="Tahoma" size="-1">You need to know some ODBC terms before plunging
into coding.</font></p>
<ul>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>Environment</b></font><font face="Tahoma" size="-1">.
It's just that, a global context in which to access data. If you are familiar
with DAO, you can think of it as a workspace. It contains information that
applies to the whole ODBC session such as the handles of connections in this
session. You must obtain the handle to environment before you can begin working
with ODBC.</font></li>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>Connection</b></font><font face="Tahoma" size="-1">.
Specify the ODBC driver and the data source (database). You can have multiple
connections to different databases in the same environment.</font></li>
<li><font color="#FFFFCC" face="Tahoma" size="-1"><b>Statement</b></font><font face="Tahoma" size="-1">.
ODBC uses SQL as its language. Thus a statement can be simply thought of as
an SQL statement you want ODBC to execute.</font></li>
</ul>
<p><font face="Tahoma" size="-1">Below are the steps you usually perform when
coding with ODBC:</font></p>
<ol>
<li><font face="Tahoma" size="-1">Connect to the data source</font></li>
<li><font face="Tahoma" size="-1">Build and execute one or more SQL statements</font></li>
<li><font face="Tahoma" size="-1">Examine the resulting records (if any)</font></li>
<li><font face="Tahoma" size="-1">Disconnect from the data source</font></li>
</ol>
<p><font face="Tahoma" size="-1">We will learn how to perform each step in the
next tutorials.</font></p>
<hr>
<p align="center"><font size="-1"><b><font face="Tahoma">[<a href="http://win32asm.cjb.net">Iczelion's
Win32 Assembly Homepage</a>]</font></b></font></p>
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