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Chapter 1

Relational Database Fundamentals

In This Chapter

▶ Organizing information

▶ Defining “database” in digital terms

▶ Deciphering DBMS

▶ Comparing database models

▶ Defining “relational database” (can you relate?)

▶ Considering the challenges of database design

QL (pronounced ess-que-ell, not see’qwl, though database geeks still

argue about that) is a language specifically designed with databases

in mind. SQL enables people to create databases, add new data to them,

maintain the data in them, and retrieve selected parts of the data. Introduced

in 1970, SQL has grown and advanced over the years to become the industry

standard. It is governed by a formal standard maintained by the International

Standards Organization (ISO).

Various kinds of databases exist, each adhering to a different model of how

the data in the database is organized.

SQL was originally developed to operate on data in databases that follow the

relational model. Recently, the international SQL standard has incorporated

part of the object model, resulting in hybrid structures called object-relational

databases. In this chapter, I discuss data storage, devote a section to how the

relational model compares with other major models, and provide a look at

the important features of relational databases.

Before I talk about SQL, however, I want to nail down what I mean by the

term database. Its meaning has changed, just as computers have changed the

way people record and maintain information.

COPYRIGHTED MATERIAL

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Pagina 1 - COPYRIGHTED MATERIAL

Chapter 1Relational Database FundamentalsIn This Chapter▶ Organizing information▶ Defining “database” in digital terms▶ Deciphering DBMS▶ Comparing da

Pagina 2 - Keeping Track of Things

16Part I: Basic Concepts Figure 1-3: Each data-base row contains a record; each database column holds a single attribute. ColumnsRowEnjoy the viewOne

Pagina 3 - Database Size and Complexity

17 Chapter 1: Relational Database FundamentalsSay, for example, that you’re working with a database that has a CUSTOMER table and an INVOICE table. Th

Pagina 4 - Management System?

18Part I: Basic Concepts shows data flowing into the accounts-payable manager’s view from both the CUSTOMER and INVOICE tables. Figure 1-5: The branch

Pagina 5 - Flat Files

19 Chapter 1: Relational Database FundamentalsSchemas, domains, and constraints A database is more than a collection of tables. Additional structures

Pagina 6 - Database Models

20Part I: Basic Concepts In the auto dealership example, you can constrain the database to accept only those four values in the Color column. If a dat

Pagina 7 - Why relational is better

21 Chapter 1: Relational Database Fundamentalscompatibility with the standard. Thus, whereas the SQL-92 standard describes a purely relational databas

Pagina 8 - Dealing with your relations

22Part I: Basic Concepts

Pagina 9

8Part I: Basic Concepts Keeping Track of ThingsToday people use computers to perform many tasks formerly done with other tools. Computers have replace

Pagina 10 - Enjoy the view

9 Chapter 1: Relational Database FundamentalsWhat Is a Database?The term database has fallen into loose use lately, losing much of its original meanin

Pagina 11

10Part I: Basic Concepts What Is a Database Management System?Glad you asked. A database management system (DBMS) is a set of programs used to define,

Pagina 12 - Part I: Basic Concepts

11 Chapter 1: Relational Database FundamentalsFlat FilesWhere structured data is concerned, the flat file is as simple as it gets. No, a flat file isn

Pagina 13 - Constraints

12Part I: Basic Concepts As you can see, the file contains nothing but data. Each field has a fixed length (the Name field, for example, is always exa

Pagina 14 - The object-relational model

13 Chapter 1: Relational Database Fundamentals ✓ Relational: These databases store their data in tables that are related to each other. Nowadays, new

Pagina 15

14Part I: Basic Concepts application is dependent on the specific physical implementation of the database. If you add a new attribute to the database,

Pagina 16

15 Chapter 1: Relational Database Fundamentalsyear, team, games played, at-bats, hits, runs scored, runs batted in, doubles, triples, home runs, bases

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