Informix Basics

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PREFACE: Introduction


This book is an introduction to the Informix product line-my world, where for over 14 years I've developed, designed, administered, and managed Informix applications. Along the way I've had the opportunity to teach Informix concepts to dozens of co-developers who have been with me in the trenches. Many times I wished I had a guidebook to make the job easier. This is that guidebook.


Who This Book is For


This book is for you if you need a tour guide through the admittedly complex suite of Informix products, or if you need a jump start to developing applications. If you are a novice programmer new to the Informix environment, you will find value here. If you are a savvy power user with plenty of ambition, this book will help launch you into the development arena. If you are experienced with other database development tools, you will find here enough universal principles to allow what you already know to be used as a springboard to your becoming a strong Informix developer.

This book is a tutorial, offering hands-on examples that will provide you a solid foundation for applications development. It does not attempt to cover every facet of the Informix product suite, but rather it distills the key concepts into manageable lessons that are directly applicable to most development efforts. Someone who knows everything between these pages is someone I'd like to have developing an application with me. When that person is you, send me e-mail to glenn@tsunami.com. We'll want to talk.


What You'll Need


This is a book describing the basic Informix product line, so you will need to havethe following basic products installed to complete the examples: an Informix database engine, Informix DB-Access, and Informix-4GL. Chapter 1, "The Informix Product Suite," describes these and other Informix components. You'll also need an experienced database administrator to install these products and instruct you how to access them. Finally, for some chapters the following software is also required: Informix-ISQL; Informix ESQL/C; UNIX Korn shell.

There are a few background skills that could make some of the material herein more familiar. A basic knowledge of structured programming concepts and operating system fundamentals would provide a good foundation. C language programming skills could also be a small plus. But if you read this book serially, letting its tutorial, stepwise examples unfold, you'll find that you have all the tools you need.


How This Book is Organized


After this Introduction, the book is organized into five parts, comprising sixteen chapters, and is followed by two appendixes. Part 1, "Getting Started," introduces the Informix product line, the relational data model, and the primary tool you will use to manipulate your databases-DB-Access. You should scan these topics even if you already have a passing knowledge of the fundamentals, if only to ensure that you build the sample music database used throughout the rest of the book.

You'll become intimately familiar with the sample database in Part 2, "SQL Fundamentals." You'll learn how to create databases and their principal components, tables. You'll see how to examine not only a database's structure, but its contents as well. You'll see how to add your own data, change it, and delete it. You'll also learn how creating simple forms and reports can simplify even these fundamental procedures.

In Part 3, "SQL Advanced Tools," you'll explore more of SQL, the industry-standard language used to interact with relational databases-the kind this book describes. You'll discover advanced ways to extract relationships from your data, and how to build queries of surprising depth. Additionally, you'll explore Stored Procedure Language, a programming tool that allows you to embed your SQL statements within procedural language rules of any complexity. This part ends as a springboard to the following one.

Part 4, "Informix Programming," shows, at length, how you can write custom Informix applications. You'll progress from building the simplest "Hello, World!" example to writing programs of surpassing complexity. You'll discover that by keeping individual parts of your programs direct and purposeful (using functions), by segregating discrete operations into isolated functions (modularity), and by incrementally building ever-larger working programs from smaller functioning components (stepwise refinement), you'll discover no practical limit to the applications you can create.

The remaining sections are bonuses. Not strictly addressing SQL or programming proper, Part 5, "Advanced Topics" and the appendixes provide complementary material that can help you become a more complete Informix developer. These topics include data migration and database administration tools, as well as how to create the sample database. While not strictly mandatory, the lessons of Part 5 can differentiate an educated programmer from an effective one. Appendix A, "The Sample Database," contains the instructions for building the database upon which the book's examples are based. Following those instructions will save you time and make the exercises clearer. Finally, Appendix B, "Administrative Tools," describes some of the ways you can look behind the scenes at your Informix databases and processes. It's a useful aside.


Conventions Used in This Book


This book uses different typefaces to help you differentiate between Informix commands and regular English, and to highlight important concepts. Actual Informix code and keywords are in a special monospace font. In examples where the input and output of a command or program are presented, the user input is typeset in bold monospace. Placeholders-terms for which you substitute values-are typeset in an italic monospace font. New or important terms are typeset in italic.

The book contains some special features to help you navigate the Informix product line. Syntax diagrams show you how to use a specific Informix command. Here is an example, from Chapter 5, "Basic SQL," describing the syntax of the update command:

update table-name
set column-name = value
, column-name = value �
where condition-list

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