Table of Contents
Database Developer's Guide with Visual C++ 4, Second
EditionImprint: SAMS Author: Roger Jennings & Peter Hipson
Publication Date: Apr-96 ISBN: 0-672-30913-0 Retail Price: $59.99
US
This book emphasizes optimization of database design;
implementing Access SQL for Access, dBASE, Paradox, and Btrieve
databases. And provides in-depth coverage of the networking issues
surrounding databases.q
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CD-ROM includes a data dictionary application, crosstab query
generator, multiform graphical front end, DDE and OLE applications
with Excel, DAO applications Gives in-depth coverage of Windows
database programming techniques Teaches all of Visual C++'s Data
Access Object features, including Jet Database Access engine
Who Should Read This Book? What's New in This Edition - I
-Visual C++ Data Access - 1 -Positioning Visual C++ in the Desktop
Database Market - 2 -Understanding MFC's Data Access Classes - 3
-Using Visual C++ Data Access Functions - II -Database and Query
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- 4 -Optimizing the Design of Relational Databases - 5 -Learning
Structured Query Language - 6 -The Microsoft Jet Database Engine -
7 -Using the Open Database Connectivity API - 8 -Running Crosstab
and Action Queries - III -An Introduction to Database Front-End
Design - 9 -Designing a Decision-Support Application - 10 -Creating
Your Own Data Access Controls - 11 -Using the New Win32 Common
Controls - 12 -Printing Reports with Report Generators - IV
-Advanced Programming with Visual C++ - 13 -Understanding MFC's DAO
Classes - 14 -Using MFC's DAO Classes - 15 -Designing Online
Transaction-Processing Applications - 16 -Creating OLE Controls
with Visual C++ 4 - 17 -Using OLE Controls and Automation with
Visual C++ Applications - 18 -Translating Visual Basic and Visual
Basic for Applications Code to Visual C++ - V -Multiuser Database
Applications - 19 -Running Visual C++ Database Applications on a
Network - 20 -Creating Front Ends for Client-Server Databases - 21
-Interacting with Microsoft Mail, MAPI, and TAPI VI - Distributing
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- 22 -Documenting Your Database Applications - 23 -Creating Help
Files for Database Applications - 24 -Creating Distribution Disks
for Visual C++ Applications - A -Resources for Developing Visual
C++ Database Applications - B -Naming and Formatting Conventions
for Visual C++ Objects and Variables - C -Using the CD-ROM
Installing the CD-ROM More Books
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What Will You Need to Use This Book? What Will You Gain from
This Book?
Who Should Read This Book?Visual C++ developers who want to take
advantage of Visual C++'s database connectivity to create
highspeed, commercial-quality graphic front ends for a variety of
desktop and client-server database applications. Access developers
who have found that they need more control over their data display
and forms than is afforded by the different versions of Access.
Visual C++ database applications also consume far fewer Windows
resources than equivalent Access applications. Visual Basic
developers who want to take advantage of Visual C++'s automated
access to the Windows APIs, gain function callback capability, and
manipulate pointers. Developers of xBase and Paradox applications
who need to create industrial-strength, 32-bit database front ends
running under Windows 95 or Windows NT 3.5x. Users and developers
of proprietary GUI front-end development systems who are tired of
paying substantial per-seat licensing fees for each client
workstation attached to the server.
What Will You Need to Use This Book?
You will need experience with Visual C++ or one of the
traditional PC programming languages for Windows, such as Microsoft
or Borland C or C++, Turbo Pascal for Windows, or the Windows
version of SmallTalk.
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You will need Microsoft Visual C++, running on Microsoft Windows
95 or Microsoft Windows NT with appropriate hardware and sufficient
resources. Prior experience in basic database design would be
helpful.
What Will You Gain from This Book?
The latest professional techniques in front-end and database
design. An arsenal of real-world solutions to speed your
development. Troubleshooting methods to put a stalled project back
on track. Detailed explanations of the theories behind the
practical solutions.
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Database Developer's Guide with Visual C++ 4, Second Edition
Copyright 1996 by Sams Publishing Acknowledgments About the Authors
Introduction What's New in Visual C++ for Database Developers s New
Features of Visual C++ A Database Developer's View of Visual C++
Visual C++ and Microsoft BackOffice Who Should Read This Book What
You Need to Use This Book Effectively How This Book Is Organized s
Part I s Part II s Part III s Part IV s Part V s Part VI s
Appendixes Conventions Used in This Book s Key Combinations and
Menu Options s Visual C++ Code, SQL Statements, and Source Code in
Other Languages s Entries in Initialization and Registration
Database Files s Visual C++ Code Examples and Code Fragments s
Prefix Tags for Data or Object Type Identification A Visual C++ and
Database Bibliography s Introductions to Visual C++ Programming s
Visual C++ Books for Developers s A Book on the Microsoft Jet
Database Engine s The Primary Guide to SQL-92 s Publishers of
Database Standards Keeping Up to Date on Visual C++ s Periodicals s
The MSDN Support Product s Microsoft Internet Services
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What's New in This Editionq
Expanded coverage of ANSI and Access SQL queries via Visual C++
4 code. Additional techniques for OLE automation. Information on
programming with the new OLE containers. Coverage of OLE Custom
Controls, which let you add new features to Visual C++ applications
with minimal programming effort. Information on OLE Custom Controls
for 32-bit environments. Techniques for using the new data access
objects that Microsoft added to Visual C++ to position the product
as a direct competitor to Visual Basic. These new techniques make
Visual C++'s support of Access, FoxPro, and Paradox for Windows in
the desktop database market even more complete. Detailed
information on the redistributable 32-bit Microsoft Jet 3.0
database engine, which offers substantially improved performance
compared to the 16-bit jet engine. Coverage of Visual C++'s
built-in MFC classes, along with AppWizard, to let you quickly
create a form to display database information with little or no
Visual C++ code. Included is a sample program that actually has no
programmer-written code at all. Information on the Microsoft ODBC
Administrator application, included with Visual C++, which lets you
connect to the Microsoft and Sybase versions of SQL Server and to
Oracle client-server relational database management systems.
Extensive coverage of building Visual C++ 4 front ends to interface
with client-server RDBMSs. Clear examples that illustrate
significant development topics, such as crosstab queries, action
queries, transaction processing, and record locking. Programming
examples and techniques for using Sockets and MAPI services.
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Peter Hipson Roger Jennings
201 West 103rd Street, Indianapolis, Indiana 46290 This book is
dedicated to Kathareeya "Katie" Tonyai, a brand new granddaughter.
Peter Hipson This book is dedicated to the memory of my father,
George H. Jennings, Structural Engineer. Roger Jennings
Copyright 1996 by Sams PublishingSECOND EDITION All rights
reserved. No part of this book shall be reproduced, stored in a
retrieval system, or transmitted by any means, electronic,
mechanical, photocopying, recording, or otherwise, without written
permission from the publisher. No patent liability is assumed with
respect to the use of the information contained herein. Although
every precaution has been taken in the preparation of this book,
the publisher and author assume no responsibility for errors or
omissions. Neither is any liability assumed for damages resulting
from the use of the information contained herein. For information,
address Sams Publishing, 201 W. 103rd St., Indianapolis, IN 46290.
International Standard Book Number: 0-672-30913-0 Library of
Congress Catalog Card Number: 95-72921 99 - 98 - 97 - 96 ----4 - 3
- 2 - 1 Interpretation of the printing code: the rightmost
double-digit number is the year of the book's printing; the
rightmost single-digit, the number of the book's printing. For
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Composed in AGaramond, Optima, Helvetica, and MCPdigital by
Macmillan Computer Publishing Printed in the United States of
America All terms mentioned in this book that are known to be
trademarks or service marks have been appropriately capitalized.
Sams Publishing cannot attest to the accuracy of this information.
Use of a term in this book should not be regarded as affecting the
validity of any trademark or service mark.
AcknowledgmentsThe authors are indebted to Neil Black of
Microsoft's Jet Program Management Group and Stephen Hecht of
Microsoft's Jet Development Group for their "Jet Database Engine
2.0 ODBC Connectivity" white paper. This white paper made a
substantial contribution to the writing of Chapter 7, "Using the
Open Database Connectivity API." You can find this white paper and
a number of other works by these authors on the Microsoft
Development Library CD. Search for the authors' names. Special
thanks to Microsoft and Steve Serdy at Microsoft Developer Support
for their excellent assistance. Steve's help with the Win32 Common
Controls was most valuable. Thanks are also due to Robert Bogue and
Jeff Perkins, the technical editors for this book. Jeff's help in
getting our references to Microsoft SQL Server 6 up-to-date was
most valuable. Thanks also to Grace Buechlein, our acquisitions
editor. Grace's professionalism was most valuable when we had
problems, and we hope to work with her again. Thanks to Michael
Watson, our development editor, for his extra work in making sure
that the book presented the very latest information available.
Thanks also to Gayle Johnson, our production editor, and to Anne
Owen, our copy editor.
About the AuthorsPeter Hipson is a developer, consultant, and
author. His work is mostly in the Windows arena, but he also
pursues work in ODBC, database, and GIS applications. He was a
member of the Microsoft beta-test team for QuickC for Windows;
Visual C++ 1.0, 1.5, 2.0, and 4.0; Windows 3.0 and 3.1; Windows 95;
Windows for Workgroups 3.1 and 3.11; and Windows NT. Peter is the
author of Sams Publishing's Advanced C, What Every Visual C++ 2
Programmer Should Know, and Visual C++ Developer's Guide, as well
as Que's Using QuickC for Windows. He was a coauthor of Database
Developer's Guide with Visual C++ and Programming Windows 95
Unleashed, both from Sams Publishing. He also occasionally writes
for the Windows Technical Journal. He will be writing a column on
database programming in The Win'95 Magazine, which will publish its
first issue in mid-1996. He also has a column in an Asian magazine
on the Internet. Peter has been working
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microcomputers since the mid-1970s. He also has many years of
experience with IBM mainframes. He is the author of STARmanager, a
GIS-type application that assists sales and marketing managers in
managing their resources. You may contact Peter via CompuServe
(70444,52) or the Internet ([email protected]). Roger
Jennings is a consultant specializing in Windows database,
multimedia, and video applications. He was a member of the
Microsoft beta-test team for Visual C++ 2.0; Visual Basic 2.0, 3.0,
and 4.0; the Professional Extensions for Visual Basic 1.0; Visual
Basic for DOS; Microsoft Access 1.0, 1.1, 2.0, and 7; Word for
Windows 2.0; the 32-bit versions of Word and Excel; Microsoft
Project 4.0 and 4.1; Windows 3.1 and Windows 95; Windows for
Workgroups 3.1 and 3.11; Windows NT 3.5, 3.51, and 4.0 Workgroup
and Server; the Microsoft ODBC 2.0 and 2.5 drivers; Video for
Windows 1.1; and Multimedia Viewer 2.0. Roger is the author of Sams
Publishing's Database Developer's Guide with Visual Basic 4, upon
which much of this book is based. He also wrote Access 2
Developer's Guide and Access 95 Developer's Guide, both from Sams
Publishing, and two other books on Microsoft Access, as well as
books devoted to Windows 95, Windows NT, and desktop video
production with Windows 95 and Windows NT 3.5x. He also is a
contributing editor for Fawcette Technical Publications' Visual
Basic Programmer's Journal. Roger has more than 25 years of
computer-related experience, beginning with his work on the Wang
700 desktop calculator/computer. He has presented technical papers
on computer hardware and software to the Academy of Sciences of the
former USSR, the Society of Automotive Engineers, the American
Chemical Society, and a wide range of other scientific and
technical organizations. He is a principal of OakLeaf Systems, a
Northern California software consulting firm. You may contact him
via CompuServe (70233,2161), the Internet
([email protected]), or the Microsoft Network
(Roger_Jennings).
IntroductionThe release of Visual C++ clearly shows that
Microsoft is taking the lead in creating C++ development platforms.
Visual C++ 4 continues to build on the development platform that
the C/C++ program has established. MFC, with versions 2.0, 2.5,
3.0, and 4, offers the C++ programmer an advanced object-oriented
methodology to develop applications that are easy to develop and
maintain. Microsoft's OLE and the Common Object Model (COM) are now
firmly entrenched as the new compound document standard for
Windows, and OLE Automation replaces DDE as the primary means of
interapplication communication. Huge system resource consumption by
OLE megaservers, typified by Excel and Word, limited the adoption
of OLE Automation in commercial database front ends. Windows 95 and
Windows NT 3.51 have overcome most resource limitations when
running 32-bit OLE applications. Thus, 32-bit Visual C++ programs
are likely to be the glue that binds industrial-strength solutions
orchestrating members of 32-bit Microsoft Office with OLE
Automation. Out-of-process OLE Automation servers, especially the
big ones, are not renowned for their speed. Fortunately, there's a
trend toward a Pentium on every power-user's desktop, so faster
hardware comes to the rescue again. OLE Custom Controls (OLE
controls), which are in-process OLE Automation servers, don't
suffer from the performance hit associated with the Lightweight
Remote Procedure Calls (LRPCs) required by out-of-process servers.
Thus, OLE controls typically are as quick as VBXs, which OLE
controls replace in the 32-bit versions of Windows.
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Microsoft's addition of the Microsoft Jet database engine's DAO
interface to MFC makes Visual C++ a strong competitor to the
principal players in the desktop database market: Access, Visual
Basic, FoxPro for Windows, Lotus Approach, and Borland
International's dBASE and Paradox for Windows. The Open Database
Connectivity (ODBC) application programming interface (API),
introduced in Visual C++, made Visual C++ a major factor in
client-server front-end development throughout the world. DAO
promises to lead Visual C++ 4 into areas that in the past have been
the private domain of Visual Basic. Using 32-bit ODBC resolves the
controversy in the computer press regarding the relative
performance of DBLib and ODBC with Microsoft SQL Server. Tests show
that 32-bit ODBC is as fast as or faster than equivalent calls to
DBLib functions. The three major sections of this Introduction
describe the new database connectivity features of Visual C++ and
show how Visual C++ fits into the database front-end and back-end
market.
What's New in Visual C++ for Database DevelopersVisual C++'s new
features of fall into two basic categories:q
Features that are of interest only to database developers
Features that affect all Visual C++ developers, regardless of
whether they use Visual C++'s Data Access Objects
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First, it is very important to realize that programmers today
use many different versions of Visual C++.q
The first version of Visual C++, 1.0, was available in both a
16-bit and a 32-bit edition. Both of these products are now
out-of-date and aren't used much by professional programmers. The
next major release of Visual C++, 1.5, was made available only in a
16-bit version. This version included MFC 2.5 and other
improvements. The 16-bit versions of Visual C++ that followed
Visual C++ 1.5 include 1.51 through 1.52. Version 1.52c is
distributed with Visual C++ 4. Microsoft distributes both versions
together to give developers of 32-bit applications access to the
16-bit development tools. The 1.5x versions of the 16-bit Visual
C++ products incorporate minor changes and additions, such as the
inclusion of the OLE controls development platform. The second
major release of the 32-bit version of Visual C++ was Visual C++ 2.
This product, released in the fall of 1994, supports only 32-bit
applications. A redesigned development environment, MFC 3, and
other features made Visual C++ 2 a major player in the 32-bit C/C++
development arena. The next release of the 32-bit version of Visual
C++ was Visual C++ 4. This product, released in the fall of 1995,
supports only 32-bit applications. MFC 4, DAO, numerous
improvements to the developer environment, and other features make
Visual C++ 4 a must-have for any serious Windows developer.
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A subscription program was offered to Visual C++ programmers who
needed regular updates to Visual C++. Originally slated to be
delivered every quarter, releases have been coming out about twice
a year. The current subscription program promises the "next two
releases," which would represent about a year in time. Microsoft
has announced that Visual C++ 4.1 should be available in the spring
of 1996. The subscription version of Visual C++ is available from
Microsoft directly and from most resellers.
There will be more releases of Visual C++ as the years go by.
However, it is beyond the scope of this book to speculate what the
future holds for Visual C++. The following sections describe the
categories of Visual C++ features.
New Features of Visual C++
The most apparent change in Visual C++ 4 for database
programmers is the adoption of MFC 4 and the addition of the MFC
Data Access Object (DAO) classes. Additionally, Windows 95's Rich
Text common control has been integrated into MFC. The following
list briefly describes the most important differences between
Visual C++ 4 and earlier versions of Visual C++:q
Visual C++ 1.5x develops 16-bit applications, whereas Visual C++
4 is a 32-bit (only) development platform. Visual C++ 4 uses a much
more advanced development environment. The integration of Visual
C++ 4's components is much tighter than it was with Visual C++ 2.
There have been major improvements to Visual C++ 4's ClassWizard,
too. This lets the programmer have docked windows, more flexible
toolbars, and other ease-of-use features. Visual C++ 4 offers MFC 4
and supports 32-bit OLE. Visual C++ 4 has integrated the
functionality of the AppStudio program (which is used to edit
program resources) into Visual C++'s development environment. There
are improved toolbar editing and design tools, and the graphics
editor is much better. For programmers who are just moving up to
the 32-bit version of Visual C++, there is no need to switch
between Visual C++ and AppStudio while developing applications.
Visual C++ 4 can edit resources in applications. You can use this
functionality, missing from Visual C++ 2, when running Visual C++ 4
under Windows NT. Visual C++ applications support toolbars, status
bars, dialog bars, and floating palettes. Toolbars are dockable and
have optional tooltip support built-in. Visual C++ supports 32-bit
OLE Custom Controls, more commonly called OLE controls in this
book. Because VBX controls can't be used in 32-bit environments,
OLE controls are your only custom control choice when creating
32-bit Visual C++ 4 applications. Third-party VBX publishers have
created a wide
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array of OLE controls, with functionality similar to their most
popular VBX controls.q
Visual C++ 4 comes with a number of useful OLE controls,
including the ever-popular Grid control, and a number of sample
controls that can be rewritten if you like. Customization lets you
alter Visual C++'s user interface by adding menu choices, modifying
toolbars, and manipulating other elements of the design
environment. Visual C++ 4 lets you configure the editor to emulate
either the Brief or Epsilon editors. Visual C++ 4 supports remote
debugging using either a network connection or serial ports.
However, there is still no support for dual-monitor debugging. You
can create out-of-process OLE miniservers (OLE applets, typified by
Microsoft Graph 5.0) that you can use with any application that can
act as an OLE Automation client, including Visual C++. Microsoft
calls these miniservers LOBjects (line-of-business objects). You
can run multiple instances of Visual C++ in order to test your
newly created OLE applet.
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A Database Developer's View of Visual C++Making the choice
between Access, Visual Basic, Visual FoxPro, Paradox for Windows,
dBASE for Windows, Delphi, or Visual C++ as your primary database
development platform is not a simple matter, especially for
seasoned developers of character-based applications. Most
programmers don't consider Visual C++ to be a database development
tool, so they adopt one or more of the popular Windows desktop
database systems or Visual Basic. FoxPro for Windows offers xBase
language compatibility and, without question, is the fastest of all
the Windows desktop databases. Access has a unique user interface
that lets you run simple to moderately complex database
applications with a minimum of effort, and it also supports OLE
controls (OCXs). Visual Basic offers more programming flexibility
than Access, and you can incorporate a variety of commercial and
shareware OLE controls to simplify database front-end development.
The Paradox for Windows desktop RDBMS has a wider variety of field
data types than any RDBMS, Windows or DOS, including client-server
database systems. Each of these products has its own feature set,
together with limitations that might not become apparent until
you're embroiled in your first large-scale client-server database
front-end application. Chapter 1, "Positioning Visual C++ in the
Desktop Database Market," compares Visual C++ to your alternatives
among the major combatants in the Windows database wars. If you've
invested several years in developing xBase or PAL programming
skills and are reluctant to abandon xBase RDBMSs or Paradox for a
new object-oriented, event-driven Windows programming language,
welcome to the crowd. COBOL programmers have the same problem when
their employers downsize from mainframe "legacy" databases to
client-server systems running on PCs. Unfortunately for PAL
programmers, the ObjectPAL programming language of Paradox for
Windows bears little resemblance to the
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PAL of Paradox. xBase and PAL, however, all have their roots in
the original Dartmouth BASIC. The C programming language has a
structure similar to PL/I or PASCAL. Thus, you might find the
structure of Visual C++ applications similar to the xBase or PAL
programs you're now writing. If only C++ were as simple as C! C is,
for the most part, easy to use, but when many programmers are
exposed to C++ for the first time, they find it to be totally
different than C. Nothing could be further from the truth, however.
C++ is easy to learn and adapt to if you remember that the original
C language is a subset of C++. The quickest conversion from C to
C++ is to simply rename the file. Simply choosing Visual FoxPro,
dBASE for Windows, or Paradox for Windows because you're accustomed
to writing xBase or PAL code isn't likely to be a viable long-term
solution to your Windows database development platform dilemma
(notwithstanding John Maynard Keynes' observation that "in the long
term, we are all dead"). If you create Windows applications for a
living, either as an in-house or independent developer, you're
expected to provide your firm or client with applications that
incorporate today's new technologies. You need to prepare now for
OLE, with its in-place activation and OLE Automation (OA), and
Visual C++ OLE controls. Windows is where the action is. More than
60 million copies of Windows (a mixture of Windows 3.x, Windows 95,
and Windows NT) give Microsoft the marketing clout to make OLE,
ODBC, and OLE controls the "standards" of the desktop computers of
the world (whether the "industry" agrees or not). The alternative
vaporware standards proposed by groups of software vendors
organized to combat the Microsoft behemoth are very unlikely to
replace OLE, ODBC, and OLE controls in the foreseeable future.
Windows desktop database applications present a challenge to
developers accustomed to writing a thousand or more lines of code
to create character-based RDBMS applications in Visual Basic,
xBase, PAL, C, or other programming languages. You can create a
very simple but usable Visual C++ database application with
AppWizard and very little Visual C++ code. One example in this book
contains no programmer-written code at all. Microsoft Access offers
code-free capabilitiesif you don't consider Access macros to be
code. You'll need to write substantial amounts of code to create a
usable database application with dBASE, Visual FoxPro's xBase, or
Paradox's ObjectPAL. However, the reality is that you have to write
a substantial amount of code to create a commercial-quality
production database application with any of these products. The
issue isn't how much code you have to write, but in which language
you will write the code. Here are some of the language issues that
will affect your career opportunities or the size of the numbers on
your 1099s:q
xBase and PAL are yesterday's most prevalent desktop database
programming languages. Will xBase and ObjectPAL ultimately survive
the onslaught of Microsoft's present Object Basic dialects, such as
Visual Basic and the Visual Basic for Applications (VBA) variants
of Microsoft Word 7, Access 7, and Excel 7? Visual C++ lets you
write incrementally compiled database applications that don't
require helper libraries such as VBRUN300.DLL. Borland's Delphi
offers fully compiled .EXEs but uses a variation of Pascal as its
programming language. Does Delphi's Pascal really stand a chance of
replacing C++ as the preferred language for writing commercial
Windows applications or of making Object Basic/VBA extinct as an
application programming (macro) language? Visual C++ 4, Access 7,
and Visual Basic 4 act as containers for OLE Custom Controls.
Excel, Word, and Project also support OLE controls. Will many of
the new applications systems that will be released in the next few
years also support OLE controls?
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Visual C++ 4 allows cross-platform development for a number of
different platforms, including applications for Macintosh
computers. Microsoft now has a Macintosh version of Visual C++ that
enables Windows developers to easily port their Windows
applications to the Macintosh. Most development done under Windows
NT can be directly ported to Windows 95 with minimum
modifications.
This book doesn't purport to answer these questions directly,
but you're likely to reach your own conclusions before you finish
reading it. At the time this book was written, Visual C++, Visual
Basic 4, and Access were the major database development platforms
to fully support OLE, OLE Automation, and OLE controls. Visual C++
is the only development platform, other than Visual Basic, that
lets you create your own OLE Automation miniservers. Chapter 16,
"Creating OLE Controls with Visual C++ 4," and Chapter 17, "Using
OLE Controls and Automation with Visual C++ Applications," describe
how OLE, OLE Automation, and OLE controls fit into your
decision-support database front ends.
NOTE Access 2 was released before the OLE Custom Control
specification was finalized and many months before the retail
release of Microsoft Visual C++ 2.0's Control Development Kit
(CDK), which developers need in order to implement OLE controls.
Access 2's OC1016.DLL isn't compatible with the final version of
commercial OLE controls designed for use with Visual C++, which use
OC25.DLL. The Access 2 Service Pack updates Access 2.0 to
accommodate 16-bit OLE controls based on Visual C++ 1.5's OC25.DLL.
If you find that you need to work with Access 2, you should keep
these restrictions in mind. Access 7 doesn't present these
problems.
Whatever language you ultimately choose, you must adapt to the
event-driven approach to application design, inherited from the
Windows graphical user interface (GUI). You also need to face the
fact that Windows applications won't perform with the blazing speed
of your Clipper or FoxPro applications running directly under DOS.
Few, if any, Windows applications can match their DOS counterparts
in a speed contest, but this situation is likely to change when you
run your 32-bit database front end under Windows NT on a
high-powered RISC workstation. Fortunately, most Windows users have
grown accustomed to the sometimes sluggish response of Windows.
It's possible, however, to design Visual C++ client-server front
ends that rival the performance of their character-based
counterparts. Chapter 15, "Designing Online Transaction-Processing
Applications," and Chapter 20, "Creating Front Ends for
Client-Server Databases," provide examples of "plain vanilla" front
ends that deliver excellent performance.
Visual C++ and Microsoft
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When this book was written, Microsoft Office (both 4.2x and
Office 95) had garnered more than 80 percent of the Windows
productivity application suite (front-end) market. Microsoft Office
4.2 includes Excel 5.0, Word 6.0, PowerPoint 4.0, and a Microsoft
Mail 3.2 client license. Microsoft Office 95 includes Excel 7, Word
7, and PowerPoint 7, all in 32-bit versions that run under both
Windows 95 and Windows NT. The Professional Versions of Microsoft
Office also include Microsoft Access (Office 4.3 contains Access
2.0, while Office 95 includes Access 7). Encouraged by the success
of Office, Microsoft introduced its server (back-end) suite,
BackOffice, in the fall of 1994. Microsoft BackOffice comprises a
bundle of the following server products:q
Microsoft Windows NT 3.51 Server, the operating system on which
the other components of BackOffice run as processes. Microsoft SQL
Server 6 , a client-server RDBMS. Will be upgraded to Microsoft SQL
Server 6.5 in the spring of 1996. Microsoft SNA Server 2.11, which
provides connectivity to IBM mainframes and AS/400 series
minicomputers via IBM's System Network Architecture. Microsoft
Systems Management Server (SMS) 1.1, which helps you distribute
software and track client hardware and software. Version 1.2 is
scheduled to be released to beta sites sometime in 1996. Microsoft
Exchange Server, which integrates e-mail, group scheduling,
electronic forms, and groupware applications on a single platform
that can be managed with a centralized, easy-to-use administration
program. It's designed to make messaging easier, more reliable, and
more scalable for businesses of all sizes. Microsoft Mail Server
3.5, a file-sharing e-mail system. Will be upgraded to Microsoft
Exchange Server when it becomes available in the spring of
1996.
q
q
q
q
q
Like Microsoft Office, you get a substantial discount (of about
40 percent) from the individual server license prices when you
purchase the BackOffice bundle. Unlike earlier versions of Windows
NT Server and SQL Server, which were available in "Enterprise"
versions with unlimited client licenses, BackOffice doesn't include
client licenses. The commercial success of BackOffice, is by no
means assured. It's not likely that large numbers of major
corporations, the target market for BackOffice, will adopt this
bundle until final versions of all of its promised components are
delivered, which might not happen until 1997. Microsoft SQL 6.0 and
Exchange Server use OLE and OLE Automation pervasively. The
Messaging API 1.0 (Extended MAPI), on which Exchange is based, uses
Messaging OLE objects, and Schedule+ 7.0 has its OLE/Schedule+
object collections. The development tools for Microsoft SQL Server
6.0 RDBMS and Exchange e-mail system use VBA. (Exchange Server is a
nonrelational database optimized for messaging services.)
Ultimately, all of the members of the BackOffice suite are likely
to offer VBA extensions for customization. Microsoft has positioned
Visual C++ as a development platform for "building solutions" based
on BackOffice servers. Visual C++ developers stand to gain a huge
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applications for Microsoft Exchange and SQL Server 6.0.
Who Should Read This BookThis book is intended primarily, but
not exclusively, for the following categories of readers:q
Visual C++ developers who want to take maximum advantage of
Visual C++'s database connectivity to create high-speed,
production-grade graphic front ends for a variety of desktop and
client-server databases. Access developers who have found that they
need more control over their data display and editing forms than is
afforded by the present version of Microsoft Access. Visual C++
database applications also consume far fewer Windows resources than
equivalent Access applications. Visual Basic developers who want to
take advantage of Visual C++'s automated access to the Windows
APIs, gain function callback capability, and manipulate pointers.
Developers of character-based DOS database applications whose
clients or organizational superiors have decided to migrate from
DOS to Windows applications. Users of xBase or Paradox products who
need to create industrial-strength, 32-bit database front ends
running under Windows 95 or Windows NT 3.51. (Windows NT 3.51 might
not yet be a major player in the operating systems numbers game,
but firms that adopt Windows NT 3.51 are major employers of
database consultants.) Programmers who would like to develop
database applications by expending less than 25 percent of the time
and effort required to create equivalent applications with C and
C++. Those addicted to C++ can quickly create prototype database
applications with Visual C++. (It's amazing how many prototype
Visual C++ applications become production database front ends.)
Victims of the corporate downsizing revolution, principally COBOL,
PL/I, or FORTRAN programmers who need to acquire C, C++, and
Windows database development skills to remain gainfully employed.
Users of proprietary GUI front-end development applications for
client-server databases who are tired of forking over substantial
per-seat licensing fees for each client workstation that is
attached to the server. Chief information officers (CIOs) or
management information services (MIS) executives who need to make
an informed decision as to which Windows front-end generator their
organization will adopt as a standard. Others who are interested in
seeing examples of commercially useful Visual C++ database
applications that earn developers a comfortable or
better-than-comfortable living.
q
q
q
q
q
q
q
q
q
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This book assumes that you have experience with Visual C++ or
one of the traditional PC programming languages for Windows, such
as Microsoft or Borland C or C++, Turbo Pascal for Windows, or the
Windows version of SmallTalk. This book doesn't contain an
introduction to C/C++ programming techniques; many excellent
tutorial and references books are available to fill this need. (The
bibliography that appears later in this Introduction lists some of
the better books and other sources of information for
beginning-to-intermediate-level C/C++ programmers.) Instead, this
book begins with an overview of how Visual C++ fits into the
desktop and client-server database market and proceeds directly to
dealing with data sources in Visual C++. The entire content of this
book is devoted to creating useful Visual C++ database
applications, and most of the examples of Visual C++ code involve
one or more connections to database(s). All the code examples in
this book, except for minor code fragments, are included on the
accompanying CD. Sample databases in each of the formats supported
by the Access 7 database engine are provided. Some of the sample
databases are quite large, so you can use their tables for
performance comparisons. Tips and notes based on the experience of
database developers with Visual C++ and Access appear with
regularity.
What You Need to Use This Book EffectivelyYou need Visual C++ 4
(or later) to re-create or modify the sample applications that
appear in this book. Although you can use Visual C++ 2.x , Visual
C++ 4 (or later) is a necessity for serious database development
using the 32-bit environment provided by Windows 95 and Windows NT,
mostly due to the fact that Visual C++ 4 supports DAO. Executable
versions of selected sample applications are included on the
accompanying CD, as are a number of programs, demos, and other
items. I strongly recommend that you purchase a copy of Microsoft
Access if you intend to use Access .MDB database files in
commercial applications. You can't really create new databases and
add tables using the ODBC drivers that are supplied with Visual
C++; however, DAO does allow the creation of Access databases. You
can use Access's query design window to create a query graphically,
test the result, and then copy the Access SQL statement underlying
the query to your Visual C++ code. Using Access's Relationships
window to establish rules for enforcing referential integrity and
creating business rules that maintain domain integrity is much
simpler than Visual C++'s code-centric approach. An additional
benefit of acquiring Access is the availability of database design
and documentation tools for Access that are not yet available to
Visual C++ database developers. Some of the new design and
documentation tools for Access databases are described in Chapter
4, "Optimizing the Design of Relational Databases," and in Chapter
22, "Documenting Your Database Applications." If you develop Visual
C++ database applications for a living, you'll save many times your
investment if you buy a copy of Access.
NOTE If you don't have Excel or Word for Windows, it might be
well worth the investment to get the Microsoft Office Professional
Edition, which includes Wordfile:///H|/0-672-30913-0/vcgfm.htm (13
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for Windows, Excel, Access, and PowerPoint.
Developers of commercial database applications with Visual C++
are likely to want the additional features offered by third-party,
data-aware custom controls. As these controls become available
(WinWidgets/32 is an example), they can save the programmer
substantial effort in developing applications. Although Microsoft
has co-opted the data-aware grid, combo box, and list box OLE
control market by providing 16- and 32-bit OLE control versions of
these controls with Visual C++ 4, many third-party publishers offer
quite useful enhancements to Microsoft's set. Several third-party
custom controls are used to create the sample applications in this
book. Sources of these OLE controls are provided in Appendix A,
"Resources for Developing Visual C++ Database Applications." Most
Visual C++ database applications for Windows 3.1+ and Windows 95
will perform satisfactorily on 80386DX/33 or faster computers with
8M or more of RAM. If you plan to use Access, you should have a
minimum of 16M of RAM. If you plan to take full advantage of OLE
and OLE Automation, 12M to 16M of RAM is recommended, regardless of
which applications you will be running. All of the 32-bit versions
of the sample applications in this book run satisfactorily under
Windows NT Workstation 3.51 with 16M of RAM, and on a Windows 95
80386DX/33 with 8M of RAM. All development work was done on a
Pentium 90 with 32M of RAM, a machine of acceptable performance.
The authors recommend running Visual C++ 4 with at least 16M of RAM
on a fast 486 (or better) processor.
How This Book Is OrganizedThis book is divided into six parts
that contain 24 chapters. Each part deals with related database
application design subjects. The parts are ordered in a way that
parallels a typical database application development program. The
contents of each part and chapter are described in the sections
that follow.
Part I
Part I, "Visual C++ Data Access," introduces you to Visual C++'s
capabilities as a Windows database application development
environment. Chapter 1, "Positioning Visual C++ in the Desktop
Database Market," analyzes the features that Visual C++ offers
database developers and shows how the language fits into
Microsoft's strategy to dominate the desktop and client-server
database development markets. Chapter 2, "Understanding MFC's ODBC
Database Classes," provides a detailed description of how you
create and manipulate Visual C++ MFC classes and collections using
Access .MDB databases. Chapter 3, "Using Visual C++ Data Access
Functions," covers the ODBC API-level SQL...() functions and
presents some functions that use the ODBC API and that can be
called from both C and C++ programs.
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Part II
Part II, "Database and Query Design Concepts," deals with
relational database design and shows you how to use SQL to create
SELECT and action queries that employ the Access database engine
and the ODBC API to process the queries. Chapter 4, "Optimizing the
Design of Relational Databases," shows you how to normalize data in
order to eliminate data redundancy in your application. Chapter 5,
"Learning Structured Query Language," discusses ANSI SQL-89 and
SQL-92 and tells how Access SQL differs from the "standard" SQL
used by client-server and mainframe databases. Chapter 6, "The
Microsoft Jet Database Engine," provides insight on the use of the
Jet ODBC drivers with xBase, Paradox, and Btrieve tables. It also
introduces you to Microsoft's Data Access Objects (DAO), a
technology newly incorporated into Visual C++ 4.0. Chapter 7,
"Using the Open Database Connectivity API," shows how Visual C++
applications interface with ODBC drivers. Chapter 8, "Running
Crosstab and Action Queries," advances beyond simple SQL SELECT
queries and shows you how to write queries that include TRANSFORM,
PIVOT, INTO, and other less commonly used SQL reserved words that
modify the data in your tables.
Part III
Part III, "An Introduction to Database Front-End Design," is
devoted to creating commercial-quality decisionsupport front ends
for databases. Chapter 9, "Designing a Decision-Support
Application," describes the principles of converting raw data into
easily comprehensible information that can be displayed on Visual
C++ forms. Chapter 10, "Creating Your Own Data Access Controls,"
shows you how to take advantage of OLE Custom Controls. Chapter 11,
"Using the New Win32 Common Controls," gives examples of using
Visual C++ with the new Win32 Common Controls in programs that will
work in both Windows 95 and Windows NT. Chapter 12, "Printing
Reports with Report Generators," shows you how to design reports
and how to seamlessly integrate report generation with your
database applications.
Part IV
Part IV, "Advanced Programming with Visual C++," takes you
deeper into the realm of commercial database application
development. Chapter 13, "Understanding MFC's DAO Classes," shows
you the new MFC 4 implementation of the Data Access Object
interface to the Microsoft Jet database engine, providing a
reference to the DAO classes. Chapter 14, "Using MFC's DAO
Classes," presents a practical tutorial dealing with the DAO
classes. Chapter 15, "Designing Online Transaction-Processing
Applications," describes how to design forms for heads-down,
high-speed data entry and how to use Visual C++'s
transaction-processing reserved words to speed bulk updates to
tables. Chapter 16, "Creating OLE Controls with Visual C++ 4,"
explains how to develop practical OLE controls. Chapter 17, "Using
OLE Controls and Automation with Visual C++ Applications,"
describes how to add OLE controls to your applications using Visual
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with Chapter 18, "Translating Visual Basic for Applications Code
to Visual C++," for Access developers who are porting Access
applications to Visual C++.
Part V
Up until Part V, "Multiuser Database Applications," this book is
devoted to self-contained applications designed for a single user.
Part V provides the background and examples you need to add
networking and client-server database capabilities to your Visual
C++ database applications. Examples employ Windows 95, Windows NT
Server 3.51, and SQL Server 6 for Windows NT. Chapter 19, "Running
Visual C++ Database Applications on a Network," describes how to
use peer-to-peer and network servers to share databases among
members of a workgroup or throughout an entire organization.
Chapter 20, "Creating Front Ends for Client-Server Databases,"
describes how to use the ODBC API to set up and connect to
client-server and mainframe data sources with your Visual C++
applications. Decision-support and online transaction processing
examples that connect Microsoft SQL Server for Windows NT are
included. Chapter 21, "Interacting with Microsoft Mail, MAPI, and
TAPI," details the use of the MAPI custom control, the Schedule+
Access Library (SAL), and TAPI. Examples of using Microsoft's
Electronic Forms Designer (EFD) to create mail-enabled Visual C++
applications are provided as well. Chapter 21 also gives you a
brief glimpse of what you can expect when you begin to develop
applications for Microsoft Exchange.
Part VI
Part VI, "Distributing Production Database Applications," shows
you that no production database application is complete without
full documentation and an online help system for users. Chapter 22,
"Documenting Your Database Applications," shows you how to use
Visual C++'s database object collections to create a data
dictionary in the form of a text file that you can import into
other applications, such as Word for Windows 7 or Excel 7. Chapter
23, "Creating Help Files for Database Applications," describes how
to use Word for Windows and commercial WinHelp assistants, such as
Doc-To-Help and RoboHelp, to speed the addition of contextsensitive
help to your Visual C++ applications. Chapter 24, "Creating
Distribution Disks for Visual C++ Applications," shows you how to
create a professional installation application that uses either the
Microsoft Setup application for Visual C++ or other mainstream
Windows setup applications.
Appendixes
The appendixes provide useful reference data. Appendix A,
"Resources for Developing Visual C++ Database Applications," lists
add-in products that offer new features to your database
applications. It also lists publishers of periodicals devoted to
Visual C++ and databases in general. Suppliers and publishers are
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subject, and entries include addresses, telephone numbers, and
fax numbers, as well as brief descriptions of the products listed.
Appendix B, "Naming and Formatting Conventions for Visual C++
Objects and Variables," describes the prefix tags used in this book
to identify the object or data type of variables. These naming
conventions are based on a slightly modified form of Hungarian
Notation that is commonly used in C and C++ programming. This
notation was invented by Charles Simonyi, who at one time worked on
the development of Access 1.0 at Microsoft. Appendix C, "Using the
CD-ROM," describes the files included on the CD that comes with
this book.
Conventions Used in This BookThis book uses several typesetting
styles to distinguish between explanatory material, the entries you
make in Windows dialog boxes, components of initialization (.INI)
files, and the code you enter in Visual C++'s code editing window.
The sections that follow describe the typographic conventions used
in this book.
Key Combinations and Menu Options
Accelerator key combinations (Alt-key) and shortcut key
combinations (Ctrl-key) that you use to substitute for mouse
operations are designated by joining the key with a hyphen (-).
Ctrl-C, for example, is the shortcut key for copying a selection to
the Windows clipboard. Alt-H is a common accelerator key
combination that takes the place of clicking the Help button in
dialog boxes. Some applications, such as Microsoft Word 6, use
multiple-key shortcuts, such as Ctrl-Shift-key, to activate macros.
Menu options are separated by a vertical bar. For example, "File |
Open" means "Choose the File menu and select the Open option."
Visual C++ Code, SQL Statements, and Source Code in Other
Languages
Visual C++ code, Visual C++ reserved words, keywords (such as
the names of collections), SQL statements, and source code
fragments in other programming languages appear in monospace type.
Reserved words and keywords in ANSI SQL and xBase programming
languages appear in uppercase monospace. Here is an example of the
formatting of an SQL statement:
SELECT Name, Address, City, Zip_Code FROM Customers WHERE
Zip_Code >= 90000
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The equivalent of the preceding statement in xBase is formatted
as
USE customers LIST name, address, city zip_code WHERE zip_code
>= 90000 The code line continuation character [ic:ccc] is used
when the length of a code line exceeds the margins of this book.
For example:
EXF=3.0;File;&Export Folder...;11;IMPEXP.DLL;0;;Exports
folders to a [ic:ccc]backup file;MSMAIL.HLP;2860 Note that this
separator character isn't a valid character when embedded in an SQL
statement String variable, nor is it valid in C/C++ source code.
Wherever possible, C/C++ code is broken so that the [ic:ccc]
character isn't needed. Some listings created by Visual C++'s
AppWizard contain lines that are too long to fit on one line of
this book. These lines are printed on two lines. When you look at
the code in an editor, however, you will see these lines as one
long line. Special implementations of SQL that don't conform to
ANSI SQL-92 standards, such as the {ts DateVariable} syntax that
Microsoft Query uses to indicate the timestamp data type, appear as
in the SQL dialog box of the application. The PIVOT and TRANSFORM
statements of Access SQL that (unfortunately) weren't included in
SQL-92, however, retain uppercase status.
Entries in Initialization and Registration Database Files
Entries in Windows, Visual C++, and Microsoft Access 2
initialization (.INI) files appear in monospace type. Sections of
.INI files are identified by square brackets surrounding the
section identifier, as in
[Options] SystemDB=c:\vbapps\system.mda Entries that you make in
Windows 3.1+'s registration database using the registration
database editor application, REGEDIT.EXE, in verbose mode also
appear in monospace to preserve indentation that indicates the
level of the entry in the tree (file-directory-like) structure of
registration database entries. The full path to HKEY_CLASSES_ROOT
and other entries in the Registry of Windows 95 and Windows NT is
provided unless otherwise indicated in the accompanying text.
Visual C++ Code Examples and Code
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As mentioned earlier, all examples of Visual C++ code, as well
as code examples, appear in monospace. Monospace type also is used
for code fragments. Styles and weights are applied to code examples
and fragments according to the following rules:q
Names of symbolic constants, including the three constants TRUE,
FALSE, and NULL, appear in uppercase. Additions to Visual C++
AppWizard-produced programs typically appear in bold monospace.
This lets you see what has been added to create the application's
functionality. Replaceable variable names, arguments, and
parameters, also known as placeholders, appear in italic monospace.
Data type identification tag prefixes that identify the data type
of variables of Visual C++'s fundamental data types and the type of
object for variables of object data types don't appear in italic,
as in int nObjectVar. French braces ({}) indicate that you must
select one of the optional elements separated by the pipe character
(|) and enclosed in the braces. This doesn't apply to the unusual
employment of French braces by Microsoft Query in SQL statements.
An ellipsis (...) indicates that the remaining or intervening code
required to complete a statement or code structure is assumed and
doesn't appear in the example.
q
q
q
q
Prefix Tags for Data or Object Type Identification
The code examples in this book use two- or three-letter prefix
tags to identify the data type of variables and symbolic constants
of the fundamental data types of Visual C++ and other Object Basic
dialects, as well as object variables. Examples of Hungarian
variable names of the fundamental data types are szStringVar,
nIntegerVar, lLongVar, dDouble, and pPointer. Microsoft and this
book use the term fundamental data type to distinguish conventional
variables, which have names that are Visual C++ reserved words,
from variables of object data types, which might have names that
are either reserved or keywords. Prefix tags also are used to
identify the type of object when you declare variables of the
various object data types supported by Visual C++. The most common
object prefix tags in this book are wsWorkSpace, dbDatabase, and
qdfQueryDef. Appendix B provides detailed information on the
derivation and use of type identifier prefix
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A Visual C++ and Database BibliographyAs I mentioned earlier,
this book is intended for readers who are familiar with writing
Visual C++, Visual Basic for Applications, and/or Access Basic
code. If your first Visual C++ application is a full-fledged
database front end, you might want to acquire one or more tutorial
or reference books on introductory or intermediate-level Visual C++
programming. Access Basic programmers who are porting Access 2 or
Access 7 applications to Visual C++ will benefit from
developer-level Visual C++ guides. You also might want more details
on the 1992 version of ANSI SQL, SQL-92, and the background of the
ODBC API. The following sections provide recommendations of
up-to-date books that fulfill these needs.
Introductions to Visual C++ Programming
The following books are designed to introduce you to Visual
C++'s event-driven graphical programming environment: Essential
Visual C++, by Mickey Williams (Indianapolis: Sams Publishing,
1995, ISBN: 0-67230787-1) Teach Yourself Visual C++ 4 in 21 Days,
by Nathan and Ori Gurewich (Indianapolis: Sams Publishing, 1994,
ISBN: 0-672-30795-2) Visual C++ in 12 Easy Lessons, by Greg Perry
and Ian Spencer (Indianapolis: Sams Publishing, 1995,
0-672-30637-9) What Every Visual C++ 2 Programmer Should Know, by
Peter Hipson (Indianapolis: Sams Publishing, 1994, ISBN:
0-672-30493-7)
Visual C++ Books for Developers
The following books cover intermediate-to-advanced Visual C++
programming topics: Develop a Professional Visual C++ Application
in 21 Days, by Mickey Williams (Indianapolis: Sams Publishing,
1995, ISBN: 0-672-30593-3)file:///H|/0-672-30913-0/vcgfm.htm (20 of
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Master Visual C++, Third Edition, by Nathan and Ori Gurewich
(Indianapolis: Sams Publishing, 1995, ISBN: 0-672-30790-1) Visual
C++ 2 Developer's Guide, Second Edition, by Nabajyoti Barkakati
(Indianapolis: Sams Publishing, 1995, ISBN: 0-672-30663-8) Visual
C++ 4 Unleashed, by Viktor Toth (Indianapolis: Sams Publishing,
1996, ISBN: 0-672-30874-6)
A Book on the Microsoft Jet Database Engine
The following book offers an excellent reference to the
Microsoft Jet database engine: Microsoft Jet Database Engine
Programmer's Guide, by Dan Haught and Jim Ferguson (Redmond:
Microsoft Press, 1996, ISBN: 1-55615-877-7)
The Primary Guide to SQL-92
If you want to fully understand the history and implementation
of the American National Standards Institute's X3.135.1-1992
standard for SQL-92, you need a copy of Jim Melton and Alan R.
Simpson's Understanding the New SQL: A Complete Guide (San Mateo:
Morgan Kaufmann Publishers, 1993, ISBN: 1-55860-245-3). Jim Melton
of Digital Equipment Corp. was the editor of the ANSI SQL-92
standard, which comprises more than 500 pages of fine print.
Publishers of Database Standards
The syntax of SQL is the subject of a standard published by the
American National Standards Institute (ANSI). At the time this book
was written, the current standard, X3.135.1-1992 or SQL-92, was
available from The American National Standards Institute 11 West
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New York, NY 10036 (212) 642-4900 (Sales Department) The SQL
Access Group (SAG) consists of users and vendors of SQL database
management systems. SAG publishes standards that supplement ANSI
X3.135.1-1989, such as the Call-Level Interface (CLI) standard used
by Microsoft's ODBC API. You can obtain SAG documents from The SQL
Access Group 1010 El Camino Real, Suite 380 Menlo Park, CA 94025
(415) 323-7992 (extension 221)
Keeping Up to Date on Visual C++A variety of sources of
up-to-date information are available to Visual C++ developers in
print and electronic formats. Both print periodicals and online
sources address management and development issues that are
applicable to database development as a whole. Several forums on
CompuServe offer product support services for Access and Windows.
The sections that follow describe some of the sources you can use
to expand your Visual C++ horizons.
Periodicals
The following are a few magazines and newsletters that cover
Visual C++ or Access, or in which articles on either appear on a
regular basis:q
Data Based Advisor is published by Data Based Solutions, Inc., a
firm related to the publishers of Access Advisor. Data Based
Advisor covers the gamut of desktop databases, with emphasis on
xBase products, but Visual C++ receives its share of coverage, too.
DBMS magazine, published by M&T, a Miller-Freeman company, is
devoted to database technology as a whole, but it concentrates on
the growing field of client-server RDBMSs. DBMS covers subjects,
such as SQL and relational database design, that are of interest to
all developers, not just those who use Visual
q
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C++.q
Smart Access is a monthly newsletter from Pinnacle Publishing,
Inc., which publishes other databaserelated newsletters and
monographs. Smart Access is directed primarily at developers and
Access power users. This newsletter tends toward advanced topics,
such as creating libraries and using the Windows API with Access
and Visual C++. A diskette is included with each issue. Windows
Watcher, Jesse Berst's (now Ziff-Davis') monthly newsletter,
analyzes the market for Windows applications, reviews new products
for Windows, and provides valuable insight into Microsoft's future
plans for Windows 95, Windows NT, and Windows applications,
including Visual C++.
q
The majority of these magazines are available from newsstands
and bookstores. Names and addresses of the publishers are listed in
Appendix A.
The MSDN Support Product
Microsoft sells three sets of subscription services available on
CD-ROM called MSDN (Microsoft Developer Network) Level I, MSDN
Level II, and MSDN Level III. Level I support consists of quarterly
disks that contain a vast amount of information and documentation.
These CDs are very valuable to all programmers. Level II support
consists of Level I and all the development tools (excluding
compilers) such as SDKs and platforms (including versions of
Windows, Windows 95, and Windows NT) that Microsoft offers,
excluding the BackOffice suite. These CDs (the count varies from
quarter to quarter, but usually there are about 20 CDs per release)
provide a firm foundation for all professional developers at a very
affordable price. Level III support includes Level II plus the
Microsoft BackOffice development system.
Microsoft Internet Services
Microsoft and other firms sponsor services on the Internet. Some
of the best support can be obtained, without charge, by using the
Microsoft Knowledge Base product, which can be accessed from the
Internet. This allows you to query the database that the Program
Support Services (PSS) people use and obtain answers to technical
questions.
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-IVisual C++ Data Access
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s
Choosing Visual C++ as Your Database Development Platform Using
Visual C++ as a Database Front End s Database Front-End Generators
s Visual C++ and SQL s Classifying Database Front-End Applications
s Database Front Ends for Decision Support s Transaction-Processing
Applications Categorizing Database Management Systems for Visual
C++ s Traditional Desktop RDBMSs s Client-Server RDBMSs s Access: A
Nontraditional Desktop RDBMS s Mainframe and Minicomputer Database
Management Systems Abandoning Traditional Database Programming
Languages s Adapting to the Windows Event-Method Environment s
Dealing with Programming Objects s The Data Types of Visual C++ The
Data Access Objects of Visual C++ s Object Collections s The Data
Control Object OLE and Visual C++ s OLE Automation s Visual Basic
for Applications Summary
-1Positioning Visual C++ in the Desktop Database MarketBetween
November 1992 and the end of 1995, Microsoft introduced a number of
new Windows relational database products: Access 7, Visual FoxPro
3.0 for Windows, and Visual C++ 4.0. Microsoft heralded Access as
"the database that anyone can use" and sold 750,000 bargain-priced
copies in 90 days when Access 1.x was first released. FoxPro for
Windows targeted existing FoxPro developers and prospective users
of Borland's long-promised dBASE for Windows. Both Access and
FoxPro targeted the market for Borland's Paradox for Windows, which
emerged shortly after the retail release of Access 1.0. Access
(upgraded to version 7.0 with the introduction of Windows 95),
Visual FoxPro, andfile:///H|/0-672-30913-0/vcg01.htm (1 of 33)
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Paradox for Windows are categorized as desktop databases. Since
its introduction, Visual Basic has had better support for database
interface than Visual C++. Only with Visual C++ 4 has the C/C++
programmer had a real interface with the Microsoft Jet database
engine. Desktop databases are applications that employ a
proprietary (native) database file or index structure (or both) and
that can be run on a PC of moderate performance (for example, an
80486 with 8M of RAM). Desktop databases also include an
application programming language that is designed specifically for
use with the native database structure. When the first edition of
this book was written, Microsoft had sold more than four million
copies of Access versions 1.0, 1.1, and 2.0. Between mid-June and
mid-November of 1995, Microsoft released Windows 95 and 32-bit
"designed for Windows 95" versions of Access (7.0), Visual FoxPro
(3.0), Visual Basic (4.0), and Visual C++ (4.0), together with the
32-bit Microsoft Office 95. Microsoft wanted to make sure that
early adopters of Windows 95 would have 32-bit applications to
run.
NOTE Access 7 for Windows 95 started shipping near the end of
1995, much later than Word 7 and Office 95.
Visual C++ is Microsoft's most extensive and powerful
programming language. Microsoft's original objective for Visual C++
was to provide a powerful and flexible platform that programmers
could use to create their own Windows applications while running
under Windows. Microsoft achieved this goal with Visual C++ 1.0.
Many experienced programmers abandoned DOS-based C, C++, and Pascal
in favor of Visual C++ because they could develop Windows
applications faster than with traditional programming languages
while working with Windows' graphical interface. Microsoft enriched
Visual C++ 1.5 with improvements in the interface and extensions to
the MFC C++ libraries, while Visual C++ 2.x moved programmers into
the 32-bit application world. Visual C++ 4.0 moves the programmer
interface, class library, and feature set to a new high. With the
introduction of Visual C++ 4.0, a new set of database features has
been added. Visual C++ 4.0 supports DAO (Data Access Objects) in
addition to ODBC and also greatly extends other support, such as
the addition of container support for OLE Custom Controls.
Independent firms have created a variety of utilities, libraries,
and add-on features for Visual C++, the majority of which addressed
database applications. There will be, in the very near future, a
plethora of new OLE Custom Controls for database programmers. By
early 1993, a Microsoft market study showed that more than 70
percent of Windows applications involved databases in one form or
another. In October of 1995, Microsoft's Visual C++ product manager
noted in a speech in Boston that between 40 and 60 percent of all
Visual C++ applications were database oriented. Visual C++ can be
expected to also be a popular database applications development
tool. Even before the introduction of Visual C++ 4.0, with its data
access objects (CRecordset, CDatabase, and CRecordView) that
greatly enhance database functionality, C and C++ were major but
unrecognized players in the Windows database market. The
introduction of Visual C++ 4.0 has now pushed Visual C++ to be a
strong competitor to Visual Basic in the database development
platform arena. The failure of market research firms to place
Visual C++ in the Windows database category caused significant
distortion of the desktop database market statistics for 1993 and
later. This chapter describes Visual C++'s role in database
application development and shows how Visual C++, OLE (Object
Linking and Embedding) automation, ODBC (Open Database
Connectivity), DAO, and MFC fit into Microsoft's strategy to
maintain its domination of the Windows application marketplace.
This chapter also discusses the advantages and drawbacks of using
Visual C++ for database applications and gives you a preview of
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covered in detail in the remaining chapters of this book. It's
becoming a 32-bit, "Designed for Windows 95" world out there, so
this book concentrates on 32-bit application development with
Visual C++ 4.0.
Choosing Visual C++ as Your Database Development PlatformVisual
C++ now includes the database connectivity and data handling
features that qualify the language as a full-fledged database
application development environment. The new data access features
that Microsoft added to Visual C++ position the product as a direct
competitor to Visual Basic and make Visual C++'s support of Access,
FoxPro, and Paradox for Windows in the desktop database market even
more complete. Visual C++'s primary advantages over its database
competitors are simplicity, flexibility, and extensibility:q
The 32-bit Microsoft Jet 3.0 database engine offers
substantially improved performance compared to 16-bit Jet 2+. Jet
3.0 is multithreaded, with a minimum of three threads of execution.
(You can increase the number of available threads by an entry in
the Windows 95 or Windows NT Registry.) Overall optimization and
code tuning also contributes to faster execution of Jet 3.0
queries. Visual C++'s built-in MFC classes, along with AppWizard,
let you quickly create a form to display database information with
little or no Visual C++ code. Chapter 2, "Understanding MFC's ODBC
Database Classes," contains a sample program that actually has no
programmer-written code at all. Visual C++ is flexible because it
doesn't lock you into a particular application structure, as is the
case with Access's multiple document interface (MDI). Nor do you
have to use DoCmd instructions to manipulate the currently open
database. Visual C++ 4.0 database front ends require substantially
fewer resources than their Access counterparts. Most 32bit Visual
C++ 4.0 database applications run fine under Windows 95 with PCs
having 8M of RAM and under Windows NT 3.51+ in the 16M range.
Microsoft says Access 95 requires 12M of RAM under Windows 95, but
you need 16M to achieve adequate performance of all but trivial
Access 95 applications. A typical Visual C++ database front-end
program would probably run with satisfactory performance on a
system with as little as 12M of RAM under Windows 95. This same
program would run well under the same amount of RAM in future
versions of Windows NT. OLE Custom Controls, not yet available in
all other database development platforms, let you add new features
to Visual C++ applications with minimal programming effort.
Third-party developers can create custom control addins to expand
Visual C++'s repertoire of data access controls. Custom controls
can take the form of OLE Custom Controls for the 32-bit
environments.
q
q
q
q
The most important benefit of selecting Visual C++ as your
primary database development platform, however, isn't evident in
Microsoft's feature list. There is a vast array of tools and
support for ODBC and database development with Visual C++ today.
Examples of the use of Visual C++ are found throughout this
book.
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Another reason for choosing Visual C++ for database application
development is its OLE compatibility. At the time this book was
written, Visual C++ was the best database development environment
that incorporated OLE. OLE automation is likely to be the most
significant OLE feature for the majority of Visual C++ database
developers. OLE automation lets you control the operation of other
OLE-compliant server applications from within your Visual C++
database application. Applications need not include Visual Basic
for Applications to act as OLE automation source applications
(servers); Word for Windows 6 and later supports OLE automation
using the conventional Word Basic macro language syntax. The
Windows database war wasn't over at the time this book was written
(heck, it may never be over), but Microsoft's multipronged attack
with Visual Basic, Access, Visual FoxPro, SQL Server, and Visual
C++ is forcing competing publishers of desktop database managers
into their defensive trenches. As a group, Microsoft's database
applications for Windows, together with ancillary products such as
ODBC, DAO, and the Access Jet database engine, have a breadth and
depth that no other software publisher presently can match.
Using Visual C++ as a Database Front EndAll of Microsoft's
32-bit mainstream Windows productivity applications and programming
languages presently support or soon will accommodate the 32-bit
Microsoft Jet 3.0 database engine. The Jet database engine is a
software component that adheres to Microsoft's Component Object
Model (COM) architecture. COM is Microsoft's infrastructure for
creating code modules (called objects) that are independent of
programming languages and computer platforms. COM defines a set of
interfaces that applications must support; OLE 2+ is a high-level
implementation of COM designed for sharing objects between Windows
applications and for application programming. OLE 2+ defines its
own set of interfaces to permit use of one program's objects by
another program. As an example, applications that support VBA, such
as Visual Basic 4.0, Access 95, Excel 95, and Project 95,
communicate with the Jet 3.0 database engine (MSJT3032.DLL) through
the Microsoft Jet 3.0 Data Access Object (DAO), DAO3032.DLL, an
in-process OLE Automation server. (Access 95 also directly calls
functions in MSJT3032.DLL). Thus, only a single copy of the Jet 3.0
DLLs is required in your \Windows\System folder; each application
creates its own instance of Jet as needed. A similar approach is
used to share other components, such as DAO, spell-checking,
graphing, and VBA 2.0; the component files are located in
subfolders of your \Windows\Program Files\Common Files\Microsoft
Shared folder if you're running Windows 95. Visual C++ is the
wildcard in the desktop database deck. Visual C++ doesn't really
have a native database structure. All four of the basic database
types supported by Visual C++ are treated the same. Microsoft
Access is simply the default database type. Visual C++ and its
Access database engine, combined with Microsoft or third-party ODBC
drivers, presently can connect to the relational database
management systems (RDBMS) listed in Table 1.1.
Table 1.1. Visual C++-compatible databases and file drivers.
Access Database Engine Drivers Microsoft ODBC Drivers Third-Part
ODBC Drivers Access (.MDB) Btrieve (.DAT) dBASE III+ (.DBF, .NDX)
Microsoft SQL Server Oracle 6 Sybase SQL Server Digital Rdb Gupta
SQLBase HP AllBase/SQL
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dBASE IV (.DBF, .MDX) FoxPro (.DBF, .CDX, .IDX) Paradox (.DB,
.PX)
Excel (.XLS)* Text (.TXT)* Access* Btrieve* dBASE III+* dBASE
IV* FoxPro 2.x* Paradox*
HP Image/SQL IBM DB2, DB2/2 IBM OS/2 DBM IBM SQL/DS Informix
Ingres NCR Teradata NetWare SQL Progress Tandem Nonstop SQL Watcom
SQL XDB
NOTE Databases and files in the Microsoft ODBC Drivers column
that are marked with an asterisk (*) are included in the Microsoft
ODBC Desktop Database Drivers kit (16-bit) and Microsoft Query.
With the exception of the ODBC driver for Rdb supplied by Digital
Equipment Corporation and the Watcom SQL driver, the third-party
drivers listed in the third column of Table 1.1 are products of
Intersolv Software. Intersolv Software offers the same collection
of ODBC drivers as Microsoft, except for the Access ODBC driver.
Other database suppliers and third-party developers supply ODBC
database drivers that you can use with Visual C++. A list of
suppliers of ODBC database drivers appears in Appendix A,
"Resources for Developing Visual C++ Database Applications."
Windows 95 currently is being shipped with no ODBC drivers. Drivers
are released from time to time by Microsoft, and Visual C++ 4.0
includes a full set of redistributable 32-bit ODBC drivers (for
both Windows 95 and for Windows NT). Some of the original Windows
NT ODBC drivers don't work well under Windows 95, so programmers
might be well advised to test their applications under both
platforms and with as many ODBC drivers as possible.
The Access database engine that is included with ODBC lets you
use dBASE III+, dBASE IV, FoxPro, Paradox, Btrieve, and Access
databases with equal facility. Microsoft's ODBC Administrator
application and the ODBC drivers created by Microsoft and
third-party developers add at least 20 additional databases and
file types to the list of those with which a Visual C++ database
application can be connected. Only Access can rival Visual C++'s
universal database connectivity. Details of the two methods of
adding database functionality to Visual C++ applications are given
in Chapter 6, "The Microsoft Jet Database Engine."
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NOTE To use Btrieve databases with Visual Basic 4.0, you need a
Windows dynamic link library (DLL) that is included with the
Btrieve for Windows application and other Btrieve products.
Appendix A of this book, "Resources for Developing Visual C++
Database Applications," provides information on how to obtain the
required Btrieve DLLs.
Borland's Paradox 7 for Windows 95 takes a tentative step in the
multidatabase direction by letting you use Paradox or dBASE files
interchangeably. If you want to, you can create a FoxPro or Paradox
application that doesn't involve a single database file. However,
you need to open an .MDB file to use Access; only a few Access
database utility functions are available before you open a new or
existing .MDB file. Included with Microsoft Office and the 16-bit
versions of Visual C++ is an add-in application, MS Query, that
lets you create new Access databases as well as add, delete, and
modify tables in new or existing Access, dBASE, FoxPro, and Paradox
databases. Figure 1.1 shows MS Query's Table window for the Orders
table of NorthWind.MDB, the sample Access database supplied with
Access. Figure 1.1. Visual C++'s data manager application, MS
Query.
NOTE Visual C++ 1.5x includes the MS Query product and a second
NWIND database; however, this example is a dBASE format database,
not an Access format. If you need a sample dBASE database, you can
use this one. Since dBASE database files aren't specific to 16-bit
or 32-bit applications, this database will work with any of the
dBASE ODBC drivers.
The Table window displays the structure of the existing fields
of a table and lets you add new fields and indexes to a table. MS
Query is an example of a Visual C++ database application that uses
MDI forms. MDI lets you create database applications with several
windows (called MDI child windows or forms) that are contained
within a conventional window (called the parent window or form).
The Microsoft ODBC Administrator application, included with Visual
C++, lets you connect to the Microsoft and Sybase versions of SQL
Server and to Oracle client-server relational database management
systems. Client-server RDBMSs are discussed later in this chapter.
You can even treat text files and Excel worksheets as database
tables by using the Microsoft ODBC Desktop Database Drivers kit.
Independent software development firms, such as Intersolv Software,
provide a variety of ODBC drivers for client-server and desktop
databases, as well as for worksheet and text files. Some of
Intersolv's ODBC drivers provide features that aren't available
when you use the Access database engine; an example is Intersolv's
capability to employ transactions with dBASE III+, IV, and 5.0
files. Figure 1.2 shows the ODBC Setup window for the Pubs sample
database of Microsoft SQL Server 4.2 running on LAN Manager 2.2.
Using ODBC drivers with Visual C++ is the subject of later sections
in this chapter and, in fact, the entire book. The Intersolv
DataDirect ODBC pack supports ALLBASE, Btrieve, CA-Ingres, Clipper,
DB2, DB2/2, DB2/6000, dBASE, Excel, FoxBase, FoxPro, Gupta SQLBase,
IMAGE/SQL, INFORMIX, InterBase, Microsoft SQL Server, Oracle,
Paradox, PROGRESS, Scalable SQL (formerly Netware SQL), SQL/400,
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Figure 1.2. The ODBC Setup window for the Microsoft SQL
Server.
NOTE If you have Visual C++ 4.0, you can distribute the
Microsoft ODBC Administrator application and the Microsoft/Sybase
SQL Server or Oracle ODBC drivers with your Visual C++
applications. The Microsoft ODBC Desktop Database Drivers kit and
Intersolv Software ODBC drivers require payment of a license fee
for distribution. Contact Microsoft Corporation or Intersolv for
the terms, conditions, and costs of distribution licenses. The file
\MSDEV\REDIST\MSVC15\REDIST\REDISTRB.WRI contains details on
distribution of the ODBC drivers. These drivers can be used with
applications under both Windows 95 and Windows NT. The 16-bit ODBC
can be used with legacy 16-bit ODBC applications under Windows 95,
but these drivers can't be used under Windows NT, nor can they be
used with 32-bit applications under Windows 95. For 32-bit
applications, Intersolv ODBC drivers look like the best alternative
when it is necessary to use non-Microsoftsupplied ODBC drivers.
Visual C++'s broad spectrum of database connectivity makes
Visual C++ an excellent candidate for developing database front-end
applications. The term database front end is used to describe a
computer application that can select items of data contained in a
database and display the chosen data items as information that is
meaningful to the user. The database system itself is called the
back end. The back-end database is, at the minimum, a collection of
related tables. Traditional desktop database managers store these
related tables as individual files in a single directory, together
with index files that are used to speed the data-gathering process.
Access and client-server RDBMS store all related tables and indexes
in a single database file. Microsoft has achieved dramatic success
in making the Windows graphical user interface (GUI) a worldwide
standard for use on corporate PCs. At the time this book was
written, Microsoft claimed to have sold more than 25 million copies
of Windows 3.x. Windows 95 earned Microsoft more than $260 million
in the quarter when it was released and more than $180 million in
the following quarter. Windows 95 was released in August of 1995.
Even in early 1995, Windows 95 had garnered enormous attention.
Thus, it's no surprise that virtually all of today's database front
ends are being created to run under Windows 95, or Windows NT. With
Visual C++ and Access, Microsoft also has the upper hand in
creating Windows database applications that employ a variety of
database structures. Wide-ranging database connectivity is one of
the major elements of Microsoft's strategy to obtain a major share
of the enterprise-wide computing market.
Database Front-End Generators
This book uses the term front-end generator to describe a
Windows application with which you can quickly create a database
front-end application for a wide variety of desktop and
client-server RDBMSs. Theoretically, any programming language that
can create executable files for Windows can qualify as a front-end
generator. You can write a
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front end by using Visual Basic, C, C++, or Pascal compilers;
and many large-scale MIS applications are written in C or C++.
Writing even a simple Windows database front end in Visual Basic,
however, requires a major programming effort that fails the
"quickly" test. Visual Basic isn't as easy to use as it is
sometimes purported to be. Thus, this book restricts the
classification of front-end generators to the following two types
of products:q
User-definable query processors let users create queries against
a variety of RDBMSs by point-and-click or dragand-drop techniques.
A query is an SQL statement that you use to select records for
display or updating. (SQL is discussed in more detail later in this
book.) Query processors don't include a programming language per
se, but many of these products provide a scripting or macro
language to automate repetitive tasks. Some query processors
include a graphical forms designer so that users can determine the
appearance of the information returned by the query. Asymetrix
InfoAssistant is a new 32-bit user-definable query processor that
can deal with a variety of desktop and client-server databases.
Channel Computing's Forest and Trees application is one of the more
popular Windows query processors. Microsoft Query, which replaces
the Intersolv add-in application included with earlier versions of
Excel, offers drag-and-drop query generation based on the methods
employed by Access's query design window. Front-end development
tools include, at the minimum, a graphical-forms designer and an
application programming language. Queries are created by using
graphical QBE (query by example) or by embedding SQL statements in
a program. One of the tests of a front-end development tool is the
product's capability to create a user-definable query processor.
Microsoft Visual C++, Access, and FoxPro qualify in this category,
as does PowerSoft Corporation's PowerBuilder. FoxPro qualifies
because FoxPro can use ODBC to connect to a variety of database
back ends.
q
More than 200 commercial Windows front-end generators were
available at the time this book was written, about evenly divided
between the two preceding categories. Most of these products also
include a report generator to print formatted data. The retail
version of Access uniquely qualifies in both categories of
front-end generators because Access's user interface (UI) is simple
enough that nonprogrammers can create their own database
applications. Presently, Access is one of Visual C++'s most viable
competitors in the front-end development tool market, as is Visual
Basic. A critical requirement of any front-end generator is the
capability to transfer data to other Windows applications easily.
Copying database information to the Windows Clipboard and pasting
the Clipboard data into a compatible application, such as Excel,
provides basic interapplication or interprocess communication (IPC)
capability. Windows DDE (dynamic data exchange) is the most
universal method of automatically transferring data to and from
database front ends; however, DDE implementations, other than
pasted dynamic links, seldom meet the "easily" part of the
requirement. Visual C++ currently offers a combination of database
connectivity and OLE compatibility.
Visual C++ and SQL
If you aren't proficient in SQL, you probably will need to learn
yet another programming language to create database front ends with
Visual C++. To select the data you want from a database attached to
a Visual C++ application, write the necessary SQL statement and
then send the statement as a string variable to the Access database
engine or an ODBC driver. SQL (properly pronounced "S-Q-L," not the
more common "sequel" or "seekel") is the lingua franca of
relational database systems. SQL has its roots in a language called
SEQUEL (Structured English Query Language), which IBM developed at
its San Jose Research Laboratory in the mid-1970s. SEQUEL later
became SEQUEL/2 and ultimately was renamed SQL. The first two
relational databases to use SQL were Oracle, developed by
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Oracle Corporation), and IBM's SQL/DS. The purpose of SEQUEL and
its successors was to provide a relatively simple, nonprocedural
programming language to manipulate relational database systems.
Visual C++ is a procedural language: You write a series of
statements, such as if...else, to instruct the Visual C++ compiler
to generate a series of instructions in a sequence you define. You
control how the program executes to achieve the result you want. A
nonprocedural language, on the other hand, expects you to write a
series of statements that describes what you want to happen, such
as SELECT * FROM TableName. The application that processes the
statement determines how the stateme
