INTRODUCTION

It has been estimated that more than 80 percent of all computer programming is database-related. This is certainly easy to believe. After all, a database can be a powerful tool for doing exactly what computer programs do best: store, manipulate, and display data.

Even many programs that seem at first glance to have little to do with traditional business-oriented data use databases to make processing easier. In fact, looking back on 40 some years of software development experience, I'm hard-pressed to think of a single nontrivial application that I've worked on that didn't use some kind of database.

Not only do databases play a role in many applications, but they often play a critical role. If the data is not properly stored, it may become corrupted, and the program will be unable to use it meaningfully. If the data is not properly organized, the program may be unable to find what it needs in a reasonable amount of time.

Unless the database stores its data safely and effectively, the application will be useless no matter how well-designed the rest of the system may be. The database is like the foundation of a building; without a strong foundation, even the best crafted building will fail, sometimes spectacularly (the Leaning Tower of Pisa notwithstanding).

With such a large majority of applications relying so heavily on databases, you would expect everyone involved with application development to have a solid, formal foundation in database design and construction. Everyone, including database designers, application architects, programmers, database administrators, and project managers, should ideally understand what makes a good database design. Even an application's key customers and users could benefit from understanding how databases work.

Sadly, that is usually not the case. Many IT professionals have learned what they know about databases through rumor, trial-and-error, tarot cards, and painful experience. Over the years, some develop an intuitive feel for what makes a good database design, but they may still not understand the reasons a design is good or bad, and they may leave behind a trail of rickety, poorly constructed programs built on shaky database foundations.

This book provides the tools you need to design a database. It explains how to determine what should go in a database and how a database should be organized to ensure data integrity and a reasonable level of performance. It explains techniques for designing a database that is strong enough to store data safely and consistently, flexible enough to allow the application to retrieve the data it needs quickly and reliably, and adaptable enough to accommodate a reasonable amount of change.

With the ideas and techniques described in this book, you will be able to build a strong foundation for database applications.

WHO THIS BOOK IS FOR

This book is intended for IT professionals and students who want to learn how to design, analyze, and understand databases. The material will benefit those who want a better high-level understanding of databases such as proposal managers, architects, project managers, and even customers. The material will also benefit those who will actually design, build, and work with databases such as database designers, database administrators, and programmers. In many projects, these roles overlap so the same person may be responsible for working on the proposal, managing part of the project, and designing and creating the database.

This book is aimed at readers of all experience levels. It does not assume that you have any previous experience with databases or programs that use them. It doesn't even assume that you have experience with computers. All you really need is a willingness and desire to learn.

WHAT THIS BOOK COVERS

This book explains database design. It tells how to plan a database's structure so the database will be robust, resistant to errors, and flexible enough to accommodate a reasonable amount of future change. It explains how to discover database requirements, build data models to study data needs, and refine those models to improve the database's effectiveness.

The book solidifies these concepts by working through a detailed example that designs a (sort of) realistic database. Later chapters explain how to actually build databases using a few different database products. The book finishes by describing topics you need to understand to keep a database running effectively such as database maintenance and security.

WHAT YOU NEED TO USE THIS BOOK

This book explains database design. It tells how to determine what should go in a database and how the database should be structured to give the best results.

This book does not focus on actually creating the database. The details of database construction are different for different database tools, so to remain as generally useful as possible, this book doesn't concentrate on any particular database system. You can apply most of the techniques described here equally to whatever database tool you use, whether it's MariaDB, PostgreSQL, SQL Server, or some other database product.

NOTE Most database products include free editions that you can use for smaller projects. For example, SQL Server Express Edition, Oracle Express Edition, and MariaDB Community Server are all free.

To remain database-neutral, most of the book does not assume you are using a particular database, so you don't need any particular software or hardware. To work through the exercises, all you need is a pencil and some paper. You are welcome to type solutions into your computer if you like, but you may actually find working with pencil and paper easier than using a graphical design tool to draw pictures, at least until you are comfortable with database design and are ready to pick a computerized design tool.

Chapters 16 through 25 build example databases using particular database offerings, so their material is tied to the databases that they demonstrate. Chapter 15, "Example Overview," introduces those chapters and lists the databases that they use.

To experiment with the SQL database language described in Chapter 26, "Introduction to SQL," and Chapter 27, "Building Databases with SQL Scripts," you need any database product that supports SQL (that includes pretty much all relational databases) running on any operating system.

HOW THIS BOOK IS STRUCTURED

The chapters in this book are divided into five parts plus appendixes. The chapters in each part are described here. If you have previous experience with databases, you can use these descriptions to decide which chapters to skim and which to read in detail.

Part I: Introduction to Databases and Database Design

The chapters in this part of the book provide background that is necessary to understand the chapters that follow. You can skim some of this material if it is familiar to you, but don't take it too lightly. If you understand the fundamental concepts underlying database design, it will be easier to understand the point behind important design concepts presented later.

Chapter 1, "Database Design Goals," explains the reasons people and organizations use databases. It explains a database's purpose and conditions that it must satisfy to be useful. This chapter also describes the basic ACID (Atomicity, Consistency, Isolation, Durability) and CRUD (Create, Read, Update, Delete) features that any good database should have. It explains in high-level general terms what makes a good database and what makes a bad database.

Chapter 2, "Relational Overview," explains basic relational database concepts such as tables, rows, and columns. It explains the common usage of relational database terms in addition to the more technical terms that are sometimes used by database theorists. It describes different kinds of constraints that databases use to guarantee that the data is stored safely and consistently.

Chapter 3, "NoSQL Overview," explains the basics of NoSQL databases, which are growing quickly in popularity. Those databases include document, key-value, column-oriented, and graph databases. Both relational and NoSQL databases can run either locally or in the cloud, but many NoSQL databases are more cloud-oriented, largely because they are newer technology so they're cloud-native.

Part II: Database Design Process and Techniques

The chapters in this part of the book discuss the main pieces of relational database design. They explain how to understand what should be in the database, develop an initial design, separate important pieces of the database to improve flexibility, and refine and tune the design to provide the most stable and useful design possible.

Chapter 4, "Understanding User Needs," explains how to learn about the users' needs and gather user requirements. It tells how to study the users' current operations, existing databases (if any), and desired improvements. It describes common questions that you can ask to learn about users' operations, desires, and needs, and how to build the results into requirements documents and specifications. This chapter explains what use cases are and shows how to use them and the requirements to guide database design and to measure success.

Chapter 5, "Translating User Needs into Data Models," introduces data modeling. It explains how to...