The Definitive DataWindow: Your Key to PowerBuilder Success

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PREFACE:

The Definitive DataWindow is the result of my long experience mentoring other PowerBuilder programmers. It doesn't follow any standard formula for teaching PowerBuilder skills. The method used in this book is the same method I use when he sits face to face with another PowerBuilder programmer and helps him understand this important object.

The book is not exactly a tutorial. Large parts of the book could be considered reference material. This material is included because it is required by the PowerBuilder developer who works with DataWindows. This book is not a reference book. In fact, it defies categorization. It is my attempt to raise the developer's understanding of this object to an advanced level. It is nothing more and nothing less.

The DataWindow is arguably the most important object in PowerBuilder. In a properly constructed application, it is the most used object. It doesn't matter what the application does; whether it is a thin-client distributed architecture application or a simple two-tier client/server, the DataWindow takes center stage in a well-designed application. This is as true of an application that is written in PowerJ or PowerSite as it is of PowerBuilder applications.

The importance of the DataWindow has led to the object being enhanced over the years. With each major revision of PowerBuilder, the DataWindow has been given the attention that it so richly deserves. Still, after almost a decade of enhancement, no book concentrates on this object and this object alone. As a result of the lack of information on this object, PowerBuilder is not used to its fullest potential. The DefinitiveDataWindow addresses that need. It provides not only the advanced skills, but the skills that you may have overlooked in your earlier studies.

Briefly stated, this book is intended to cement the programmer's DataWindow skills, picking up omissions that were made along the way, before he progresses to the newer technologies that are on the horizon and that will be strongly affected by his understanding of the DataWindow.

So exactly who should read this book? Why, the PowerBuilder, PowerJ, and/or the PowerSite programmer and any programmer using one of those design tools. Programmers at all levels can learn something from this book. While writing this book, I have asked the best PowerBuilder programmers to review my work. Without exception, each one has learned something. Personally, I learned so much that I was astonished at the breadth of the object.

I begin this study of DataWindows at the logical place: relational databases and SQL. This is the foundation of DataWindows. Without a certain understanding of the source of your data, you will never be able to optimize the retrieval of your DataWindow. You will always be held back by this limitation. Remember, should your DataWindow take a long time to return data to your application, then your DataWindow will be perceived as inefficient and sluggish no matter how efficient or elegant your design. The first few chapters of this book will help you to identify and overcome those problems.

After this, the details of the Database Painter are explored. A complete understanding of this tool provides the programmer the skills to automate the conventions that a corporation may want to establish regarding such things as edit masks and display formats. It further provides the skills to create custom versions of them.

Following this, the DataWindow control is discussed at a high level. It is here that the programmer learns such things as how to implement the undo feature. The theory of different development methodologies is discussed at this point.

Only after all this preparation does the programmer begin to explore the DataWindow itself. The strengths and weaknesses of each type of DataWindow are covered to give the programmer a better idea of how to make informed decisions concerning these objects. The needs of the eventual user of the application under construction are covered here.

After this, developers are led once again to the DataWindow control. This time, they are exposed to techniques that make use of their enhanced understanding of the DataWindow object. This results in a skill level that is far above the ordinary. It is here that the programmer begins to develop advanced skills not only in programming and database interaction, but also in user interface design.

Following this is a special chapter on graphing, an area that is often overlooked by programmers. Using graphs requires a unique set of skills that most programmers fail to learn. The skills aren't difficult, but there is little explanation of how to understand graphs. By the end of this chapter, the developer will be able to create graphs and even animate them in response to user actions. This skill alone can result in dynamic presentations.

Once all of this is finished, the programmer is brought into the world of object-oriented programming techniques with an introduction to an ancestor of the DataWindow. After reading this chapter, the programmer is no longer restricted to the considerable power of the DataWindow but can, in fact, enhance what is already there, creating a complete library of specialized DataWindows to enhance his development efforts.

Nearing the finish line now, advanced tips and techniques gleaned from years of experience overcoming real-world problems are presented in a large chapter devoted exclusively to these advanced pragmatic concerns.

While I was writing the book, PowerBuilder version 7 was released, and it became clear that Sybase intends the DataWindow to hold the same position of prominence and importance in both PowerJ and PowerSite. That meant that other chapters had to be written to cover these tools as well.

Finally, the book is rounded out with a glossary that defines terms that are so often misunderstood.

This book doesn't leave you with just theory. Included in this book are literally hundreds of lines of source code taken directly from existing programs that are running in real-life applications, not contrived examples that don't address your concerns in the real world. I wouldn't want you to feel deprived though, so I've included an example application filled with contrived code on the CD that's included with this book.

To help the programmer further understand the book, literally hundreds of screen snapshots and diagrams are also included in the book.

In other words, I have made every effort to provide a thorough treatise on the DataWindow object. If you work your way through this book, you will not only have a firm grasp of the DataWindow object—all the way to the advanced level—but you also will have a firm foundation upon which to build and incorporate cutting edge technology.

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