# Introduction SQL is the most widely used database language. Whether you are an application developer, database administrator, web application designer, mobile app developer, or a user of popular data reporting tools, a good working knowledge of SQL is an important part of interacting with databases. This book was born out of necessity. I had been teaching Web application development for several years, and students were constantly asking for SQL book recommendations. There are lots of SQL books out there. Some are actually very good. But they all have one thing in common: for most users they teach just too much information. Instead of teaching SQL itself, most books teach everything from database design and normalization to relational database theory and administrative concerns. And while those are all important topics, they are not of interest to most of us who just need to learn SQL. And so, not finding a single book that I felt comfortable recommending, I turned that classroom experience into the book you are holding. Sams Teach Yourself SQL in 10 Minutes will teach you SQL you need to know, starting with simple data retrieval and working on to more complex topics including the use of joins, subqueries, stored procedures, cursors, triggers, and table constraints. You’ll learn methodically, system- atically, and simply—in lessons that will each take 10 minutes or less to complete. Now in its fifth edition, this book has taught SQL to almost a half million English- speaking users, and has been translated into over a dozen other languages too so as to help users the world over. Now it is your turn. Turn to Lesson 1, and get to work. You’ll be writing world-class SQL in no time at all. ## Who Is the Teach Yourself SQL Book For? This book is for you if * You are new to SQL. * You want to quickly learn how to get the most out of SQL. * You want to learn how to use SQL in your own application development. * You want to be productive quickly and easily in SQL without having to call someone for help. ## DBMSs Covered in This Book For the most part, the SQL taught in this book will apply to any Database Management System (DBMS). However, as all SQL implementations are not created equal, the following DBMSs are explicitly covered (and specific instructions or notes are included where needed): * IBM DB2 (including DB2 in the cloud) * Microsoft SQL Server (including Microsoft SQL Server Express) * MariaDB * MySQL * Oracle (including Oracle Express) * PostgreSQL * SQLite ### Conventions Used in This Book This book uses different typefaces to differentiate between code and regular English, and also to help you identify important concepts. Text that you type and text that should appear on your screen is presented in monospace type. ``` It will look like this to mimic the way text looks on your screen. ``` The text that makes up programming code has no color. But most tools used to create and edit code (in all programming languages, including SQL) do display code in color. The reason for doing so is that this makes it easier to read long code sequences, and it also helps spot typos and errors (when colors don’t match or look right you know something is wrong). The SQL code throughout this book is printed in color with different colors used for SQL statements, clauses, strings, numbers, comments, and so on. Just be aware that there is no standard way to color code and different tools use different color schemes, so the colors you see in your own editor while trying the examples may not exactly match what’s in the book. This arrow (➥) at the beginning of a line of code means that a single line of code is too long to fit on the printed page. Continue typing all the characters after the ➥ as though they were part of the preceding line. > NOTE: A Note presents interesting pieces of information related to the surrounding discussion. > TIP: A Tip offers advice or teaches an easier way to do something. > CAUTION: A Caution advises you about potential problems and helps you steer clear of disaster. > PLAIN ENGLISH:New Term icons provide clear definitions of new, essential terms.