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

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 DAVIDSON has 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 KLINE is 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

) and TopXML (). He fre-
quently speaks to SQL Server and .NET user groups around Florida. Scott lives
in
W
ellington, 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

■
KURT WINDISCH is the applications supervisor for the internal IT department
at Levi, R
ay, 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 pr
esented at confer
ences internationally on the topic of
database programming with SQL Server.
xvii
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About the Technical Reviewers
■
WAYNE SNYDER is 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) (