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Chapter 1

Introduction to Database Management

Database Management

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Objectives

Provide a general introduction to the field of database management

Introduce basic terminology Describe the advantages and

disadvantages of database processing Provide a brief history of database

management Describe the hierarchical and network

database models

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Introduction

Chapter uses the example of Henry, the owner of four bookstores

Current file system is difficult and costly to use

Interested in different categories of data, called entities, including books, authors, publishers, and branches, and the relationships between these entities

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Henry’s Basic Data

File - an organized collection of data about a single entity

Record - pertains to a specific person, place, thing, or event

Fields - contain certain facts about that specific person, place, thing, or event

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Figure 1.1Branch File

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Figure 1.2Publisher and Author Files

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Figure 1.3Book File

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Figure 1.4Book-Author and Book-Branch Files

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Using a Database Management System (DBMS)

A DBMS is a program or collection of programs whose function is to manage a database on behalf of the people who use it.

Database design is the determination of the structure of the database.

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Figure 1.5Branch Form

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Figure 1.6Book Form

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Figure 1.7Book Report

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Figure 1.8Main Switchboard

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Figure 1.9Maintain Data Switchboard

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Entities, Attributes, and Relationships

Entity – a person, place, thing, or event Attribute – a property of an entity

For the entity “Person,” attributes could include eye color and height

Relationship – an association between entities Publishers are related to the books they

publish, and a book is related to its publisher

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Figure 1.10Entities and Attributes

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Figure 1.11One-to-Many Relationship

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Files and Databases

Data file – stores information on a single entity and the attributes of that entity

Database – a structure that can store information about multiple types of entities, the attributes of these entities, and the relationships among the entities

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Database Management System (DBMS)

DBMS programs manipulate databases either for the user, or a program the user is executing

Mainframe DBMSs have been used since the 1960s

Since the mid-1980s, DBMSs on PCs possess many of the features of their mainframe counterparts

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Figure 1.12Using Database Management Systems

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Database Processing

Database processing – the data to be processed are stored in a database and the data in the database are being manipulated by the DBMS

Nondatabase approach Duplication of data Extremely difficult to fulfill requirements

that involve data from more than one system

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Figure 1.13Nondatabase Approach

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Database Processing

Database approach Common database managed by a DBMS Each entity appears only once in the

system, reducing the duplication of data With all data being in a single database, it

is possible to list all information concerning the entities

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Figure 1.14Database Approach

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Figure 1.15Advantages of Database Processing

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Advantages ofDatabase Processing

Getting more information from the same amount of data When all the data for various systems are

stored in a single database, the information becomes available, as well as the process of retrieving the information can be quick and easy

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Advantages ofDatabase Processing

Sharing of data Several users can have access to the

same piece of data Balancing conflicting requirements

A person or group, often called Database Administration/Administrator (DBA) can structure the database in such a way that it benefits the entire organization, not just a single group

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Advantages ofDatabase Processing

Controlling redundancy Not only saves space, but makes the

updating process easier Consistency

Consistency is a direct result of redundancy, so by reducing redundancy, there is much less potential for this sort of inconsistency with the database approach

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Advantages ofDatabase Processing

Integrity An integrity constraint is a rule that must

be followed by data in the database Example: Not allowing a person’s age to be

lower than zero

Security The prevention of access to the database

by unauthorized users

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Advantages ofDatabase Processing

Increasing productivity A good DBMS comes with many features

that allow users to gain access to data without having to do any programming at all

Data independence A property that allows the structure of a

database to be changed without the programs that access the database having to change

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Figure 1.16Disadvantages of Database Processing

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Disadvantages ofDatabase Processing

DBMS size DBMSs are large programs that occupy a

large amount of disk space as well as internal memory

DBMS complexity The complexity and breadth of the

functions provided by a DBMS make it a complex product to use

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Disadvantages ofDatabase Processing

Greater impact of a failure A failure on the part of any one user that

damages the database in some way may affect all the other users on the system

More difficult recovery If the database is being updated by a large

number of users, all updates must be redone since the time of its restoration

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History ofDatabase Management

IBM developed the Generalized Update Access Method (GUAM) in 1964 for North American Rockwell, the prime contractor for the APOLLO project

GUAM was made available for the general public under the name Data Language/I (DL/I) in 1966

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History ofDatabase Management

DL/I became the data management component for the Information Management System (IMS), which was the dominant DBMS for many years

In the mid-1960s, General Electric developed Integrated Data Store (I-D-S)

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History ofDatabase Management

The COnference on DAta SYstems Languages (CODASYL) tackled the problem of providing standards for DBMSs in the late 1960s

In 1971, the CODASYL standards were presented to the American National Standards Institute (ANSI)

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History ofDatabase Management

Throughout the 1970s, the relational model was the subject of intense research

The 1980s is when the first commercial relational DBMSs appeared

The 1980s saw the development of object-oriented database management systems (OODBMSs)

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Hierarchical and Network Databases

Four types of data models Network Hierarchical Relational Object-oriented

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Network Model

Perceived by the user as a collection of record types and relationships between these record types

I-D-S and other CODASYL systems are examples of DBMSs that conform to the network data model

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Figure 1.17Network Database Structure

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Hierarchical Model

Perceived by the user as a collection of hierarchies, or trees

More restrictive structure than a network model

GUAM, DL/I, and IMS are examples of DBMSs that conform to the hierarchical model

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Figure 1.18Hierarchical Database Structure