The Concepts of Database Managements

1
The Concepts of Database Managements

• Chapter 1 Introduction to Database Management

2
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

3
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

4
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

5
Henrys Basic Data
Fields
Author File
Book File
Records
Publisher File
6
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

7
Non-Database Approach to Data Storage
Class Programs
Class Files
Advising Files
Advising Programs
Intramural Programs
Intramural Files
8
Disadvantages of the Non-Database Approach

• Separated and Isolated Data
• Data Duplication
• Application Program Dependency

9
Disadvantages of the Non-Database Approach

• Separated and Isolated Data
• Each application has its own private files and
  users have little opportunity to share data
  outside their own application
• Data Duplication
• Since applications are usually developed
  independently, unplanned duplicate data files are
  the rule rather than the exception. Example The
  same data may be represented in different
  applications by different names.

10
Disadvantages of the Non-Database Approach

• Application Program Dependency
• File descriptions are stored within each
  application program that accesses a given file.
  Any changes made to the file structure requires
  changes to the files descriptions as well.
• Incompatible Files
• Even if different applications can share their
  data, the files might be structures in
  incompatible formats and not allow the files to
  be read by the other application.

11
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.

12
Database Management Approach to Data Storage
Class Programs
Database Class Files Advising Files Intramural
Files
Advising Programs
DBMS
Intramural Programs
13
Advantages of the Database Management Approach
to Data Storage

• Getting More Information From the Same Amount of
  Data
• Sharing of Data
• Balancing Conflicting Requirements
• Controlled and/or Eliminated Duplication

• Consistency
• Data Integrity
• Improved Security
• Increased Productivity
• Program/Data Independence

14
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

15
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

16
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

17
Advantages ofDatabase Processing

• Data 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

• Data Security

• The prevention of access to the database by
  unauthorized users

18
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

19
Disadvantages of the Database Approach

• DBMS Size
• DBMS Complexity
• Greater Impact of a Failure
• More Difficult Recovery

20
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

21
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

22
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

23
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)

24
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)

25
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)

26
Hierarchical and Network Databases

• Four types of data models
• Network
• Hierarchical
• Relational
• Object-oriented

27
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

28
Figure 1.17 Network Database Structure
29
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

30
Figure 1.18 Hierarchical Database Structure
31
Relational Database Model

• 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

32
Relational Database Model Database Keys
Primary Key An attribute, or a collection of
attributes that uniquely identify each
Record(row) in an Entity (table)
Foreign Key An attribute, or a collection of
attributes, in one Entity whose values must match
the values of the primary key of some other
Entity.
33
Relational Database Model Relationships
Entity 1 (PRIMARY KEY, ATTRIBUTES.)
Entity 2 (PRIMARY KEY, FOREIGN KEY, ATTRIBUTES.)
34
Henrys Basic Data
35
Henrys Basic Data
36
A Relation (database table) Is?

• Singled Value Entries
• Attributes have distinct names
• All column values are of the same attribute

• Order of attributes does not matter
• Each record is distinct
• Order of the records does not matter

37
Relational Database Shorthand
Table Name(Primary Key, Attributes.., Foreign
Keys )
Book (Book Code, Title, Publisher Code, Author
Number) Author (Author Number, Name) Publisher
(Publisher Code, Name, City)
38
Components of a Database System
Developers
Database Class Files Advising Files Intramural
Files
Application Programs
Users
Application Programs