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taking time to go through this book and providing valuable feedback.
From Sanjay
My heartfelt thanks to my coauthor Alan for his outstanding technical skills, and for
his constant cooperation during the writing of this book. Special thanks to Jonathan
for not only editing this book, but also for providing me with remote access to his
Oracle9idatabase.
My adventure with Oracle started in the Tribology Workbench project at Tata Steel,
Jamshedpur, India. Sincere thanks to my co-workers in the Tribology Workbench
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Preface
project for all the experiments and explorations we did during our learning days with
Oracle. Special thanks to Sarosh Muncherji, the Deputy Team Leader, for picking me
up for the project and then pushing me into the Oracle world by assigning me the
responsibility of being the DBA. Ever since, Oracle database technology has become
a way of life for me.
Sincere thanks to my co-workers at i2 Technologies for support and encouragement.
Last, but not the least, I thank my wife, Sudipti, for her support, understanding, and
constant encouragement.
From Alan
I would like to thank my coauthor Sanjay and my editor Jonathan Gennick for shar-
ing my vision for this book, and for their technical and editorial prowess. I would
never have reached the finish line without your help and encouragement.
Most of all, I would like to thank my wife, Nancy, for her support, patience, and
encouragement, and my daughters, Michelle and Nicole, for their love and inspiration.
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Chapter 1: Introduction to SQL
Some people feel that DDL is the sole property of database administrators, while
database developers are responsible for writing DML statements, but the two are not
so easily separated.It is difficult to efficiently access and manipulate data without an
understanding of what data structures are available and how they are related; like-
wise, it is difficult to design appropriate data structures without knowledge of how
the data will be accessed.That being said, this book deals almost exclusively with
DML, except where DDL is presented in order to set the stage for one or more DML
examples. The reasons for focusing on just the DML portion of SQL include:
• DDL is well represented in various books on database design and administra-
tion as well as in SQL reference guides.
• Most database performance issues are the result of inefficient DML statements.
• Even with a paltry four statements, DML is a rich enough topic to warrant not
just one book, but a whole series of books.
*
So why should you care about SQL? In this age of Internet computing and n-tier
architectures, does anyone even care about data access anymore? Actually, efficient
storage and retrieval of information is more important than ever:
• Many companies now offer services via the Internet.During peak hours, these
services may need to handle thousands of concurrent requests, and unaccept-
able response times equate to lost revenue.For such systems, every SQL state-
ment must be carefully crafted to ensure acceptable performance as data
volumes increase.
• We can store a lot more data today than we could five years ago.A single disk
array can hold tens of terabytes of data, and the ability to store hundreds of ter-
abytes is just around the corner.Software used to load or analyze data in these
environments must harness the full power of SQL in order to process ever-
increasing data volumes within constant (or shrinking) time windows.
Hopefully, you now have an appreciation for what SQL is and why it is important.
The next section will explore the origins of the SQL language and the support for the
SQL standard in Oracle’s products.
A Brief History of SQL
In the early 1970s, an IBM research fellow named Dr.E.F.Codd endeavored to apply
the rigors of mathematics to the then-untamed world of data storage and retrieval.
Codd’s work led to the definition of therelational data modeland a language called
* Anyone who writes SQL in an Oracle environment should be armed with the following three books: a refer-
ence guide to the SQL language, such asOracle SQL: The Essential Reference(O’Reilly), a performance-tun-
ing guide, such asOracle SQL Tuning Pocket Reference(O’Reilly), and the book you are holding, which
shows how to best utilize and combine the various features of Oracle’s SQL implementation.
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DSL/Alpha for manipulating data in a relational database.IBM liked what they saw,
so they commissioned a project called System/R to build a prototype based on
Codd’s work.Among other things, the System/R team developed a simplified ver-
sion of DSL called SQUARE, which was later renamed SEQUEL, and finally
renamed SQL.
The work done on System/R eventually led to the release of various IBM products
based on the relational