Apress - Pro SQL Server 2008 Relational Database Design and Implementation (2008)02

Nearly all of Louis’s professional experience has been with Microsoft SQL Server, from the early days to the latest version currently in beta.. He spent five years serving on the board o

Character Strings 619

char[(length)] 619

varchar[(length)] 620

varchar(max) 621

text 622

Unicode Character Strings: nchar, nvarchar, nvarchar(max), ntext 622

Binary Data 623

binary[(length)] 623

varbinary[(length)] 624

varbinary(max) 624

image 625

Other Datatypes 625

rowversion (a.k.a timestamp) 625

uniqueidentifier 626

cursor 629

table 629

sql_variant 632

Not Simply Scalar Datatypes 633

■ INDEX 635

■C O N T E N T S

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Database design is a passion that Louis and I share This fall, I will be fortunate to share a stage with

my friend, Louis Davidson We’re copresenting at DevLink in Louis’s hometown of Nashville and then

again at PASS in Seattle Both times, we’ll discuss, debate, and celebrate the topic of database design

and how critical it is for any datacentric application

Database design is part science and part art There’s a science to normalization, but determining the scope of the entity is an art form best learned from working with a broad repertoire of databases

There’s a simple beauty to an elegant solution Louis is more than an author or database designer;

Louis is a master artisan, and in this book, you’ll discover hidden within the words a call to improve

your craft, to sculpt databases that stand the test of time, and to create virtual worlds of data that

enable developers to play their best game

Database design is the foundation of every datacentric application An elegant database design makes the data obvious and easy to query and sets up the developer for success with efficient

set-based queries But, no amount of code can compensate for a poor database design or add features

missing from the database No role is more critical to any datacentric application than the role of

the data modeler User interfaces come and go, but data lasts for generations of application

lan-guages, and today’s database schema errors will be cursed by programmers not yet born using

languages and tools not yet invented It’s worth spending a little extra time to polish your database

design under the tutelage of my good friend, Louis

So it’s with great pleasure that I welcome you to this third edition of Louis’s field guide to the greatest job in the world of software

Paul Nielsen

SQL Server MVP

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About the Author

■ LOUIS DAVIDSONhas over 15 years of experience as a corporate database

developer and architect Currently, he is the data architect for the

Christ-ian Broadcasting Network and NorthStar Studios in Nashville, Tennessee

Nearly all of Louis’s professional experience has been with Microsoft SQL

Server, from the early days to the latest version currently in beta Louis has

been the principal author on four editions of a book on database design

Louis’s primary areas of interest are database architecture and coding in

T-SQL, and he has experience designing many databases and writing

thousands of stored procedures and triggers through the years

About the Contributing Authors

■ KEVIN KLINEis the technical strategy manager for SQL Server solutions at

Quest Software A Microsoft SQL Server MVP since 2004, Kevin is a founding

board member and past president of the international Professional

Associa-tion for SQL Server (PASS) He has written or cowritten several books

including SQL in a Nutshell (O’Reilly, 2004), Pro SQL Server 2005 Database

Design and Optimization (Apress, 2006), and Database Benchmarking:

Practical Methods for Oracle & SQL Server (Rampant, 2007) Kevin contributes

to SQL Server Magazine and Database Trends and Applications and blogs at

SQLBlog.com and SQLMag.com Kevin is also a top-rated speaker at

confer-ences worldwide, such as Microsoft Tech Ed, the PASS Community Summit, Microsoft IT Forum,

DevTeach, and SQL Connections, and has been active in the IT industry since 1986

■ SCOTT KLEIN is an independent consultant with a passion for all things

SQL Server, NET, and XML He is the author of several books, including

Professional SQL Server 2005 XML (Wrox, 2006) and Professional LINQ (Wrox,

2008), and he writes the biweekly feature article for the SQL PASS Community

Connector He has also contributed articles for several web sites, including

Wrox (http://www.wrox.com) and TopXML (http://www.topxml.com) He

fre-quently speaks to SQL Server and NET user groups around Florida Scott lives

in Wellington, Florida, and when he is not sitting in front of a computer, he

can be found hanging out with his family or aboard his Yamaha at the local

motocross track He can be reached at ScottKlein@SqlXml.com

■ KURT WINDISCHis the applications supervisor for the internal IT department

at Levi, Ray, and Shoup, Inc., a global provider of technology solutions with

headquarters in Springfield, Illinois He has more than 17 years of experience

in the IT industry He spent five years serving on the board of directors for the

Professional Association for SQL Server, has written for several SQL Server

magazines, and has presented at conferences internationally on the topic of

database programming with SQL Server

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About the Technical Reviewers

■ WAYNE SNYDERis recognized worldwide as a SQL Server expert and Microsoft Most Valued

Professional (MVP), and he has over 25 years of experience in project management, database

administration, software design, performance measurement, and capacity planning He is a

sought-after speaker, consultant, writer, and trainer Wayne is the current president of the

Professional Association for SQL Server (PASS) (www.sqlpass.org) and a managing consultant for

Mariner, a business intelligence company (www.mariner-usa.com) He also plays keyboard for a

regional cover band named SoundBarrier (www.soundbarrierband.com)

■ EVAN TERRYis a lead consultant working at The Clegg Company, specializing in data modeling,

data quality, and information management His past and current clients include the State of Idaho;

Albertsons; American Honda Motors; and Toyota Motor Sales, USA He is the coauthor of Apress’s

Beginning Relational Data Modeling (2005) and was a presenter at the 2006 and 2007 IAIDQ

confer-ences and at the 2008 DAMA International Conference on the subject of data quality He can be

reached at evan_terry@cleggcompany.com

■ DON WATTERSis a Staff Software Engineer at the Walt Disney Internet Group in Seattle, Washington

He has been working on Microsoft SQL Server products since version 6.5, and has over 10 years of

experience with the product He has extensive administrative and developer experience with very

large OLTP and OLAP systems and enjoys learning and applying his knowledge to new and

interest-ing database challenges In his free time, Don enjoys spendinterest-ing time with his children, playinterest-ing music

and video games, and of course, studying all things related to Microsoft SQL Server He can be

reached at DonRWatters@aol.com

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If I have seen further, it is by standing on the shoulders of giants.

—Sir Isaac Newton

Iam not a genius, nor am I some form of pioneer in the database design world I acknowledge that

the following “people” have been extremely helpful in making this book happen Some helped me

directly, while others probably don’t even know that this book exists Either way, they have all been

an important part of the process

Far above anyone else, Jesus Christ, without whom I wouldn’t have had the strength to

com-plete the task of writing this book: I know I am not ever worthy of the love that You give me

My wife Valerie Davidson and daughter Amanda Davidson for putting up with this craziness for

a fourth time (and helping me with the picture for the cover) My mom for just being there to keep me entertained with information about the world around her, and my mother-in-law, too, for helping us out at times

My best friend in the world who got me started with computers back in college when I still wanted

to be a mathematician I miss him far more than he will probably ever know; some day, I need to find him again and thank him where he might actually see it

My mentors Mike Farmer, Chip Broecker, and Don Plaster for the leadership they gave me in

my early years

Gary Cornell for giving me a chance to write the book that I wanted to write.

Frank Castora and Don Watters for doing beta reads of the book on their own time (Don later

became a full technical editor on the book!) Evan Terry and Wayne Snider for their technical edits, even if the process when a little off center and didn’t end up as we started

My current manager Rob Murdoch for giving me time to go to several conferences that really helped me to produce as good of a book as I did All of my coworkers at CBN and the now-defunct Compass, who gave me many examples for the book

Scott Klein, Kevin Kline, and Kurt Windisch for taking up the slack with topics I didn’t want to

(OK, couldn’t) tackle

Paul Nielsen for offering and taking the time to write a foreword to this book.

The fantastic editing staff I’ve had, including Jonathan Gennick who (figuratively) busted my lip a few times over my poor use of the English language and without whom the writing would sometimes appear to come from an illiterate baboon Most of these people are included on the copyright page, but I want to say a specific thanks to Tony Davis (who had a big hand in the book last time) for making this book great, despite my frequently rambling writing style

Raul Garcia, who works on the Microsoft SQL Server Engine team, for information about using

EXECUTE AS and certificate-based security

Isaac Kunen for the discussions at Tech Ed that helped me understand spatial datatypes better.

James Manning for the advice on READ COMMITTED SNAPSHOT.

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Chuck Heinzelman for being such a good friend and giving me the chance to write the article

for SQL Server Standard around the time of this book coming out

All the MVPs that I’ve worked with over the past year and a half Never a better group of folks have I found Steven Dybing, Ben Miller, and now Ali Brooks have been great to work with I want to list a few others individually for things they’ve specifically done to help me out: Dejan

Sarka and Andrew Watt reviewed the previous version of the book with incredible vigor and

didn’t let me slide on even small points Hugo Kornelis gave me the most negative criticism of the previous version of the book; he really opened my eyes to some of the weaknesses (if only I could have gotten him to as one of the technical reviewers!) Steve Kass gave me the code for demonstrating what’s wrong with the money datatypes, as well as cool solutions to problems in

newsgroups that made me think Erland Somarskog helped me understand a bit more about

how error handling works, and many other topics (not to mention providing his great website,

http://www.sommarskog.se/) Adam Machanic helped me with many topics on my blog and in

newsgroups Aaron Bertrand deserves thanks for his great website http://www.aspfaq.com and the shoe memories Thanks to Kalen Delaney for all she has done for me and the community and to Dr Greg Low for putting me on his http://www.sqldownunder.com podcast Kim Tripp

provided a wonderful paper on SNAPSHOT isolation levels, and Arnie Rowland got me the two

gigs with Microsoft Learning that helped me out in parts of the book Thanks to Allen White for the times at Tech Ed and the horrible interview and to Jason Follas for the time at Tech Ed where I listened to you talking about the spatial types I also want to thank Tony Bain, Hillary

Cotter, Mike Epprecht, Geoff Hiten, Tom Moreau, Andrew Kelly, Tony Rogerson, Linchi Shea, Paul Nielson, Tibor Karaszi, Greg Linwood, Peter Debetta, Dr Tom Moreau, Dan Guzman, Jacco Schalkwijk, Anith Sen, Jasper Smith, Ron Talmage, Christian Lefter, and Kent Tegels, because all

of you have specifically helped me out over the past years in the newsgroups, teaching me new things to make my book far better

To the academics out there who have permeated my mind with database theory, such as

E F Codd, Chris Date, Fabian Pascal, Joe Celko, my professors at the University of Tennessee

at Chattanooga, and many others: I wouldn’t know half as much without you And thanks to

Mr Date for reviewing Chapter 1; you probably did more for the next version of this book

than the current one

And to Jim Gray and Ken Henderson, who both were amazing advocates of SQL Server and have inspired me over the years

Even with this large number of folks I have mentioned here, I am afraid I may have missed someone If so, thank you!

Louis Davidson

■A C K N O W L E D G M E N T S

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Ioften ask myself, “Why do I do this? Why am I writing another edition of this book? Is it worth it?

Couldn’t I help Mario save the princess faster if I just chucked the book and played Nintendo?” These

questions were answered again for me by a fellow MVP at the Microsoft MVP Summit in 2008 He

thanked me for writing this book and said that he’d tried to read the academic books on the subject

and they were hard for him to follow

“Oh yeah,” I thought, “that was why I started out to do this thing in the first place.” When I was first getting started designing databases, I learned from a few great mentors, but as I wanted to

progress, I started looking for material on database design, and there wasn’t much around The best

book I found was Chris Date’s An Introduction to Database Systems (Addison Wesley, 2003), and I

read as much as I could comprehend The problem, however, was that I quickly got lost and started

getting frustrated that I couldn’t readily translate the theory of it all into a design process that really

is quite simple once you get the ideas down In Chris’s book, and in other textbooks I had used, it

became clear that a lot of theory, and even more math, went into creating the relational model

If you want to be a theorist, Chris’s book is essential reading, along with lots of other books (here

is a good place to start looking for more titles: http://www.dbdebunk.com/books.html) The problem

is that most of these books have far more theory than the average practitioner wants (or will take the

time to read), and they don’t really get into the actual implementation of a real database system

My book’s goal is simply to fill that void and bridge the gap between academic textbooks and the

purely implementation-oriented books that are commonly written on SQL Server—my intention is

not to knock those books, not at all; I have numerous versions of those types of books on my shelf

This book is more of a technique-oriented book than a how-to book teaching you the features of

SQL Server I will cover many the most typical features of the relational engine, giving you techniques

to work with I can’t, however, promise that this will be the only book you need on your shelf

If you have previous editions of this book, you might question why you need this edition, and I know the feeling I spent a lot of time trying to figure out why you should buy this new edition, and

my reason isn’t the obvious one—that now I cover 2008 features Clearly, that is a part of it, but the

biggest thing is that I continue to come up with new content to make your job easier I’ve added

another chapter about patterns of development (Chapter 7), and every chapter has a good amount

of new material to help enhance your database designs

Oscar Wilde, the poet and playwright, once said, “I am not young enough to know everything.”

It is with some chagrin that I must look back at the past and realize that I thought I knew everything

just before I wrote my first book, Professional SQL Server 2000 Database Design It was ignorant,

unbridled, unbounded enthusiasm that gave me the guts to write the first book In the end, I did

write that first edition, and it was a decent enough book, largely due to the beating I took from my

technical editing staff And if I hadn’t possessed the enthusiasm initially that drove me to finish, I

likely would not be writing this fourth edition of the book However, if you had a few weeks to burn

and you went back and compared each edition of this book, chapter by chapter, section by section,

to the current edition, you would notice a progression of material and a definite maturing of the

writer

There are a few reasons for this progression and maturity One reason is the editorial staff I have had over the past two versions: first Tony Davis and now Jonathan Gennick Both of them were very

tough on my writing style and did wonders for the structure of the book Another reason is simply

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