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More About This Textbook
Overview
This latest edition of the best-selling implementation guide to the Structured Query Language teaches SQL fundamentals while providing practical solutions for critical business applications. The Practical SQL Handbook, Fourth Edition now includes expanded platform SQL coverage and extensive real-world examples based on feedback from actual SQL users.
The Practical SQL Handbook begins with a step-by-step introduction to SQL basics and examines the issues involved in designing SQL-based database applications. It fully explores SQL’s most popular implementations from industry leaders, Oracle, Microsoft, Sybase, and Informix.
Highlights include:
A bonus CD-ROM contains a time-limited, full-feature version of the Sybase® Adaptive Server Anywhere™ software as well as the sample database, scripts, and examples included in the book.
The Practical SQL Handbook is the most complete reference available for day-to-day SQL implementations.
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Product Details
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Meet the Author
Judith S. Bowman has been a database professional since the early 1980s. She is currently an independent consultant specializing in SQL and relational database issues and is the author of Practical SQL: The Sequel (Addison-Wesley, 2001). Sandra L. Emerson is an independent consultant and former Vice President of Publishing Programs for Sybase. Marcy Darnovsky, teaches at colleges throughout the San Francisco Bay area. She was formerly at Sybase.
Read an Excerpt
Chapter 4: Selecting Data from the Database
In This ChapterSELECT Overview and Syntax
In many ways, the SELECT statement is the real heart of SQL. It lets you find and view your data in a variety of ways. You use it to answer questions based on your data: how many, where, what kind of, even what if. Once you become comfortable with its sometimes dauntingly complex syntax, you'll be amazed at what the SELECT statement can do.Because SELECT is so important, five chapters focus on it:
- This chapter begins with the bare bones: the SELECT, FROM, and WHERE clauses, search conditions, and expressions.
- Chapter 5 delves into some SELECT refinements: ORDER BY, the DISTINCT keyword, and aggregates.
- Chapter 6 covers the GROUP BY clause, the HAVING clause, and making reports from grouped data. Chapter 6 also summarizes the issues regarding null values in database management.
- Chapter 7 introduces multiple-table queries with a comprehensive discussion of joining tables.
- Chapter 8 moves on to nested queries, also known as subqueries.
Queries in this chapter use single tables so that you can focus on manipulating the syntax in a simple environment. Following is an example of a SELECT query—don't worry about the syntax yet:Basic SELECT Syntax
Discovering the structure of the SELECT statement begins with this skeleton:Select_list and Search_condition Expressions Both the SELECT and WHERE clauses (in the select_list or search_conditions) can include
- Plain column names )
- Column names combined with other elements, such as calculations *1.085 )
- Constants (character strings or display headings)
Collectively, these are expressions. Because the column name expression is the simplest case, examples often start there and then go on to a more complex expression. This does not mean that a column name is not an expression— it's just the place to start looking at expressions. Syntax that includes "expression" or "expr" or "char_expr" means that you can use a column name or a more complex expression....Combining SELECT, FROM, and WHERE Artful combinations of the SELECT, FROM, and WHERE clauses produce meaningful answers to your questions and keep you from drowning in a sea of data. Think of the SELECT and WHERE clauses as horizontal and vertical axes on a matrix. (Figure 4.1 illustrates the query you saw at the beginning of the chapter.) The data you get from the SELECT statement is at the intersection of the SELECT (column) and WHERE (row) clauses.
Let's look at a SELECT statement with another bookbiz table, authors . The authors table stores information about authors: ID numbers, names, addresses, and phone numbers. If you want to know just the names of authors who live in California (not their addresses and phone numbers), use the SELECT clause and the WHERE clause to limit the data that the SELECT statement returns.
Here's a query that uses the SELECT clause's select_list to limit the columns you see. It lists just the names for the authors, ignoring their ID numbers, addresses, and phone numbers....
Table of Contents
Preface.
Introduction.
1.SQL and Relational Database Management.
2. Designing Datases.
3. Creating and Filling a Database.
4. Selecting Data from the Database.
5. Sorting Data and Other Selection Techniques.
6. Grouping Data and Reporting from it.
7. Joining Tables for Comprehensive Data Analysis.
8. Structuring Queries with Subqueries.
9. Creating and Using Views.
10. Security, Transactions, Performance, and Integrity.
11. Solving Business Problems.
Appendix A: Syntax Summary for the SQL Used in This Book.
Appendix B: Industry SQL Equivalents.
Appendix C: Glossary.
Appendix D: The 'bookbiz' Sample Database.
Preface
Why New Editions?
Many things have changed since this book was first published in 1989, and SQL is no exception. The SQL language has expanded tremendously, both in numbers of users and in numbers of commands. Sales of relational databases continue to rise at a strong and steady rate.When we wrote the first edition of The Practical SQL Handbook, the American National Standards Institute (ANSI) had already approved the 1986 SQL standard. The International Standards Organization (ISO) adopted it in 1987. Both ANSI and ISO helped create the 1989 version. The 1986 standards were skimpy, lacking features that most commercial vendors offered. The 1989 standards were more complete but still left many important elements undefined.
For the first edition, we felt we should focus on industry practice: As always, each vendor was keeping a wary eye on what the others were doing and making core offerings similar enough to attract both customers migrating from competitors, as well as new users looking for database systems they could build on. Because of this, we left both the not-quite-jelled ANSI standards and particular vendor implementations to the experts in those fields and concentrated on the common ground: generic or "industry-practice" SQL. Our goal was to offer the intelligent amateur practical information on how to use the actually available SQL of that time.
The 1992 ANSI standard (often called SQL-2 or SQL-92) represented a new stage in SQL development. This standard was more comprehensive than the 1989 standard: In written form it contained more than four times as many pages as the earlier version. Database vendors have adopted large parts of the 1992 standard. With the widespread adoption of the SQL-92 standard, the industry practice and the ANSI/ISO standards began to converge.
Despite vendor-specific differences, there is a general, industrywide core of SQL commands that all users need to understand. Adopting standards doesn’t happen overnight; it is a long process. At any point, vendors will have varying levels of conformance and will continue to produce vendor-specific variations. This book aims to give SQL users a mastery of the fundamentals of the language, with a side glance at the specifics of particular implementations.
Changes for Recent Editions
The changes for recent editions have been threefold:Include More Real-World Examples
In talking to new and developing SQL users, we heard over and over of their need for more examples to follow, change, narrow, and broaden. Accordingly, the bulk of the added material in the second edition consisted of code "recipes." Chapter 11, Solving Business Problems, is a selection of code samples based on questions and answers that came over computer newsgroups. We reproduce interesting problems and solutions in terms of the sample bookbiz database used throughout the book. The chapter includes examples of using the CASE function for conditional logic, formatting results, and finding date data. A few samples fall into a different category. They aren’t so much solutions to problems as indications of common errors. They include issues with DISTINCT and misunderstandings of what SQL can do.Emphasize SQL-92
With the third edition, we revised the book to incorporate the SQL-92 features that most vendors had adopted. These include new datatypes, additions to the CREATE TABLE statement that allow built-in integrity constraints, modifications to the ORDER BY and GROUP BY clauses, the new escape character for the LIKE keyword, and changes to GRANT and REVOKE, among others.Provide Software for Hands-On Practice
With the fully usable trial version of Sybase’s Adaptive Server Anywhere (ASA) on the CD that accompanies this book, you can run the examples (and your variants) on a PC. We’ve always felt that the secret to learning SQL is practice. Now you can experiment to your heart’s content, trying out code samples with data you know and checking the results to see if they are what you expect. When you’re stumped by complicated code, break it into small, meaningful pieces and run the pieces separately to make sure you understand what each segment does. Then put them together in increasingly complex combinationsand have fun!The Sybase Adaptive Server Anywhere software on the CD is a 60-day full-feature version that allows you to create objects as well as to query existing objects. ASA is built with an updated version of the bookbiz database: For the fourth edition, we increased book prices and made dates more recent. Also included on the CD are scripts to create the database on ASA (in case you damage the original) and on the other systems discussed in the book.
The Fourth Edition
The Practical SQL Handbook, Fourth Edition, continues to focus on industry-practice SQL, but the information included is at once more general and more specific than earlier editions. For the fourth edition, we had two objectives:Test on More Systems
For the fourth edition, all examples were run on five systems (Sybase Adaptive Server Anywhere, Adaptive Server Enterprise, Microsoft SQL Server, Oracle, Informix), rather than on Sybase systems only, as in the third edition. This expanded test base makes the information more universal. We are no longer limited to what we can explore or verify on a particular system. If an important feature doesn’t exist on Adaptive Server Anywhere (ASA, the RDBMS included on the CD), we can show code and results from Oracle or SQL Server.Show Examples of Vendor-Specific Differences
On the other hand, this edition is more specific. It includes information on specific idiosyncrasies of the five SQL dialects, warning readers where to look for differences. In this, it reflects the real worldlots of database users are working with multiple systems, either sequentially or simultaneously. Interesting SQL differences are flagged as SQL Variants, in-text sections that show details of differences in SQL use by different vendors. For example, how single and double quotes are used, or database users added, or outer joins specified. You won’t see code for every one of the five systems every time, but you’ll get an introduction to the kind of differences that are likely in a particular area.Acknowledgments
We would like to thank the following people for their contributions to this book: Donna Jeker and Stu Schuster for supplying timely support and encouragement; Jeff Lichtman and Howard Torf for offering advice, examples, anecdotes, and reality checks; Tom Bondur, Susie Bowman, John Cooper, and Wayne Duquesne for providing resource materials and other information; Paul Winsberg for reviewing the database design chapter in the first edition; Robert Garvey for technical review of the second edition; Karen Ali for facilitating the third edition’s SQL Anywhere CD; and Theo Posselt for technical review of the third edition.For the fourth edition, we would like to acknowledge Mike Radencich of iAnywhere Solutions (a Sybase Company), for providing the software and permissions for the Adaptive Server Anywhere CD; Lance Batten of Tilden Park Software and Sanford Jacobs of Paragon Software for comments and corrections; our reviewers, on whom we rely for timely and detailed feedback: Vijayanandan Venkatachalam, curriculum director of Oracle Corporation; David McGoveran of Alternative Technologies; Roger Snowden; Amy Sticksel of Sticksel Data Systems; Paul Irvine of Emerald Solutions; and Karl Batten-Bowman.
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