Introduction to Database Management

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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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Henrys 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 1.1 Branch File
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Figure 1.2 Publisher and Author Files
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Figure 1.3 Book File
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Figure 1.4 Book-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 1.5 Branch Form
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Figure 1.6 Book Form
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Figure 1.7 Book Report
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Figure 1.8 Main Switchboard
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Figure 1.9 Maintain 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 1.10 Entities and Attributes
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Figure 1.11 One-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 1.12 Using 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 1.13 Nondatabase 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 1.14 Database Approach
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Figure 1.15 Advantages 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 persons 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 1.16 Disadvantages 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 1.17 Network 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 1.18 Hierarchical Database Structure