Databases Demystified a self teaching guide phần 1 doc

Since then he has been continuously employed in a widevariety of information technology positions, including programmer, programmer/analyst, systems architect, project manager, senior da

DATABASES DEMYSTIFIED

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DOI: 10.1036/0071469605

To everyone from whom I have learned so much about so many things, including the many teachers, students, and co-workers

I have had the pleasure of knowing.

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ABOUT THE AUTHOR

Andrew J (Andy) Oppel is a proud graduate of The Boys’ Latin School of land and of Transylvania University (Lexington, KY) where he earned a BA in com-puter science in 1974 Since then he has been continuously employed in a widevariety of information technology positions, including programmer, programmer/analyst, systems architect, project manager, senior database administrator, databasegroup manager, consultant, database designer, and data architect In addition, he hasbeen a part-time instructor with the University of California (Berkeley) Extensionfor over 20 years, and received the Honored Instructor Award for the year 2000 Histeaching work has included developing two courses for UC Extension, “Concepts ofDatabase Management Systems” and “Introduction to Relational Database Man-agement Systems.” He also earned his Oracle 9i Database Associate certification in

Mary-2003 He is currently employed as the principal data architect for Ceridian, a leadingprovider of human resource solutions Aside from computer systems, Andy enjoysmusic (guitar and vocals), amateur radio (Pacific Division vice director, AmericanRadio Relay League), and soccer (referee instructor, U.S Soccer)

Andy has designed and implemented hundreds of databases for a wide range ofapplications, including medical research, banking, insurance, apparel manufactur-ing, telecommunications, wireless communications, and human resources His da-tabase product experience includes IMS, DB2, Sybase, Microsoft SQL Server,Microsoft Access, MySQL, and Oracle (versions 7, 8, 8i, and 9i)

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CONTENTS AT A GLANCE

CHAPTER 2 Exploring Relational Database Components 25

CHAPTER 6 Logical Database Design Using

CHAPTER 9 Connecting Databases to the Outside World 227

CHAPTER 12 Databases for Online Analytical Processing 293

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The Object-Oriented Model 15The Object-Relational Model 16

CHAPTER 2 Exploring Relational Database Components 25

Conceptual Database Design Components 26

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QBE: The Roots of Forms-Based Queries 52Getting Started in Microsoft Access 52The Microsoft Access Relationships Panel 55The Microsoft Access Table Design View 57Creating Queries in Microsoft Access 59Example 3-1: List All Customers 62Example 3-2: Choosing Columns to Display 63Example 3-3: Sorting Results 64Example 3-4: Advanced Sorting 66Example 3-5: Choosing Rows to Display 66Example 3-6: Compound Row Selection 68Example 3-7: Using Not Equal 70Example 3-8: Joining Tables 70Example 3-9: Limiting Join Results 72Example 3-10: Outer Joins 75Example 3-11: Multiple Joins;

Demystified / Databases Demystified / Oppel/ 225364-9 / FM

Getting Started with Oracle SQL 91

Finding Database Objects Using Catalog Views 97Viewing Database Objects Using

Oracle Enterprise Manager 98Data Query Language (DQL):

Example 4-1: Listing All Employees 100Example 4-2: Limiting Columns to Display 100Example 4-3: Sorting Results 102Choosing Rows to Display 103

Data Manipulation Language (DML) 114Transaction Support

Data Definition Language (DDL) Statements 118The CREATE TABLE Statement 118The ALTER TABLE Statement 119The CREATE VIEW Statement 121The CREATE INDEX Statement 121

Data Control Language (DCL) Statements 122

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Applying the Normalization Process 148

First Normal Form: Eliminating

TLA University Academic Tracking 164Composite Default screen

Computer Books Company 170

Entity Relationship Modeling 180

The Function Hierarchy Diagram 192

Relating Entities and Processes 196

Integrating Business Rules and Data Integrity 214

Referential (Foreign Key) Constraints 216

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Connecting Databases to the Web 235Introduction to the Internet and the Web 236Components of the Web “Technology Stack” 238Invoking Transactions from Web Pages 239Connecting Databases to Applications 240Connecting Databases via ODBC 240Connecting Databases to Java Applications 241

Other Client Considerations 257

Database Security Architectures 259

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I owe much to my parents for providing me with an excellent education and a love of

both learning and teaching I credit The Boys’ Latin School of Maryland and the late

Jack H Williams, headmaster, with teaching me to write effectively And I credit

Transylvania University and Dr James E Miller for introducing me to the fascinating

world of information systems and providing me with the tools for continuous learning

I’d like to thank the wonderful people at McGraw-Hill/Osborne for the opportunity to

write my first book and for their excellent support during the writing process Finally,

my thanks to my wife Laurie and our sons Keith and Luke for their support, patience,

and understanding during the long hours it took to produce this book

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Thirty years ago, databases were found only in special research laboratories where

computer scientists struggled with ways to make them efficient and useful, and

pub-lished their findings in countless research papers Today databases are a ubiquitous

part of the information technology (IT) industry and business in general We directly

and indirectly use databases every day—banking transactions, travel reservations,

employment relationships, web site searches, purchases, and most other

transac-tions are recorded in and served by databases

As with many fast-growing technologies, industry standards have lagged behind

the development of database technology, resulting in a myriad of commercial

prod-ucts, each following a particular software vendor’s vision Moreover, a number of

different database models have emerged, with the relational model being the most

prevalent Databases Demystified examines all of the major database models,

in-cluding hierarchical, network, relational, object-oriented, and object-relational

However, Databases Demystified concentrates heavily upon the relational and

ob-ject-relational models because these are the mainstream of the IT industry and will

likely remain so in the foreseeable future

The most significant challenge in implementing a database is designing the

struc-ture of the database correctly Without a thorough understanding of the problem the

database is intended to solve, and without knowledge of the best practices for

orga-nizing the required data, the implemented database becomes an unwieldy beast that

requires constant attention Databases Demystified focuses on transformation of

re-quirements into a working database model with special emphasis on a process called

normalization, which has proven to be an effective technique for designing

rela-tional databases In fact, normalization can be applied successfully to other database

models And, in keeping with the notion that you cannot design an automobile if you

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have never driven one, the SQL language is introduced so that the reader may

“drive” a database before delving into the details of designing one

I’ve drawn on my extensive experience as a database designer, administrator, andinstructor to provide you with this self-help guide to the fascinating and complexworld of database technology Examples are included using both Microsoft Accessand Oracle Publicly available sample databases supplied by these vendors (theMicrosoft Access Northwind database and the Oracle Human Resources databaseschema) are used in example figures whenever possible so that you may try the ex-amples directly on your own computer system A review quiz is provided at the end

of each chapter along with a comprehensive exam at the end of the book

If you have any comments, I’d like to hear from you

Andrew J (Andy) Oppelandy@andyoppel.comHonored instructor, University of California Berkeley ExtensionPrincipal data architect, Ceridian

Certified Oracle 9i Database Associate

xx Databases Demystified

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CHAPTER 1

Database Fundamentals

This chapter introduces fundamental concepts and definitions regarding databases,

including properties common to databases, prevalent database models, a brief

his-tory of databases, and the rationale for focusing on the relational model

Properties of a Database

A database is a collection of interrelated data items that are managed as a single unit

This definition is deliberately broad because there is so much variety across the

vari-ous software vendors that provide database systems Microsoft Access places the

entire database in a single data file, so an Access database can be defined as the file

that contains the data items Oracle Corporation defines their database as a

collec-tion of physical files that are managed by an instance of their database software

product An instance is a copy of the database software running in memory

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Microsoft SQL Server and Sybase define a database as a collection of data items thathave a common owner, and multiple databases are typically managed by a single in-stance of the database management software This can be quite confusing if youwork with multiple products because, for example, a database as defined by MicrosoftSQL Server and Sybase is exactly what Oracle Corporation calls a schema

A database object is a named data structure that is stored in a database The cific types of database objects supported in a database vary from vendor to vendorand from one database model to another Database model refers to the way in which

spe-a dspe-atspe-abspe-ase orgspe-anizes its dspe-atspe-a to pspe-attern the respe-al world The most common dspe-atspe-abspe-asemodels are presented in “Prevalent Database Models,” later in this chapter

A file is a collection of related records that are stored as a single unit by an ing system Given the unfortunately similar definitions of files and databases, howcan we make a distinction? A number of Unix operating system vendors call theirpassword file a “database,” yet database experts will quickly point out that, in fact, it

operat-is not Clearly, we need a bit more rigor in our definitions The answer lies in an derstanding of certain characteristics or properties that databases possess that ordi-nary files do not, including the following:

un-• Management by a Database Management System (DBMS)

• Layers of data abstraction

• Physical data independence

• Logical data independenceThese properties are discussed in the following subsections

The Database Management System (DBMS)

The Database Management System (DBMS) is software provided by the databasevendor Software products such as Microsoft Access, Oracle, Microsoft SQLServer, Sybase, DB2, INGRES, and MySQL are all DBMSs If it seems odd to youthat the acronym used is DBMS instead of merely DMS, keep in mind that the term

“database” was originally written as two words, and by convention has become asingle compound word

The DBMS provides all the basic services required to organize and maintain thedatabase, including the following:

• Moving data to and from the physical data files as needed

• Managing concurrent data access by multiple users, including provisions toprevent simultaneous updates from conflicting with one another

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