ITS232
Introduction To Database Management Systems
CHAPTER 1
Database Concepts
Siti Nurbaya Ismail
Faculty of Computer Science & Mathematics,
Universiti Teknologi MARA (UiTM), Kedah
| sitinurbaya@kedah.uitm.edu.my | http://www.sitinur151.wordpress.com |
| A2-3039 | ext:2561 | 012-7760562 |
1
Chapter 1: Database Concepts
1.0 Database Concepts
1.1 Introducing The Database
1.2 The Historical Roots Of Database
1.3 Files And File Systems
1.4 A File System Critique
1.5 Database Systems
1.6 Database Models
2
1.1 Introducing The Database
1.1.1 Data and information
 Data?
– Raw facts
– Building blocks of information
– Examples:
• NURUL JANNAH ALI
• 2009256966
• CS113
3
1.1 Introducing The Database
1.1.1 Data and information
 Information?
– Produce by processing data
– Reveal meaning of data
– Examples:
• 2009256996 is NURUL JANNAH ALI
UiTM Metrics Number and currently she is studying
in CS113 Program at UiTM Kedah
4
1.1 Introducing The Database
1.1.1 Data and information
How do data and information relate?
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1.1 Introducing The Database
A Glance of Database Concept
subject
student
register
subjectno
description
registerID
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name
ITS232
Database
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ITS232
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Literature
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ITS232
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Farah
2009451782
Thohier
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1.1 Introducing The Database
1.1.2 What is database?
Database
 A shared collection of integrated computer structure designed to
meet various needs of an organization.
–
It houses:
• End-user-data : raw facts
• Metadata
: data about data
DBMS
 DataBase Management System
 A software that enable user to define, create, maintain and control
access to database
–
–
–
Possible to share data among multiple applications or users
Makes data management more efficient and effective
Examples:
• IBM DB2, MS Access, MySQL, ORACLE
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1.1 Introducing The Database
1.1.2 What is database?
Create
Database
Retrieve
Data
DBMS
Create
Forms
allows
Sort Data
Create
Reports
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1.1 Introducing The Database
1.1.2 What is database?
The importance of database:





Manage interactions between end users and database
Helps make data management more efficient and effective
Its query languages allows make quick answers to add-hoc queries
Provide end users better access to more and better managed data
Promote and integrated view of org’ operations big picture
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1.1 Introducing The Database
1.1.2 What is database?
Advantages of database:












control of data redundancy
data consistency
more information from the same amount of data
sharing of data
improved data integrity
improved security
enforcement of standards
economy of scale
improved data accessibility and responsiveness
increased productivity
improved maintenance through data independence
improved backup and recovery services
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1.1 Introducing The Database
1.1.2 What is database?
Disadvantages of database:







complexity
size (space)
cost of DBMS
additional hardware cost
cost of conversion
performance
higher impact of failure
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1.1 Introducing The Database
1.1.3 Types of database
Database can be classifieds into three types, they are:
Classified by number of user
Classified by used
Classified by locations
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1.1 Introducing The Database
1.1.3 Types of database
Types 1: Classified by number of user
• Single-user
• Supports only one user at a time
• Desktop
• Single user database, running on a personal computer
• Multi-user
• Supports multiple user at one time
• Workgroup
• supports a small group of user on a single department
• Enterprise
• supports a large group of users on entire organization
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1.1 Introducing The Database
1.1.3 Types of database
Types 2: Classified by used
• Transactional / Production
• Support immediate responses transaction
• Company day-to-day transaction
• Data warehouse
• Stores data used to generate information required to make
tactical or strategic decisions
• Often used to store historical data
• Provided by decisions support system (DSS), data
massaging (data manipulation) to extract information
from historical data
• Data warehouse describe dB design by DSS
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1.1 Introducing The Database
1.1.3 Types of database
Types 3: Classified by locations
• Centralized dB
• DBMS that supports a database located at a single site
• Distributed dB
• DBMS that supports a database distributed across several
different sites
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1.1 Introducing The Database
1.1.4 Why db are valuable assets for decision making?
 Basically, database stored data, process data into information as
needed by end-user (company)
 Accurate, relevant, and timely information is key to good decision
making
 Good decision making is the key to survival in a global environment
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1.1 Introducing The Database
1.1.5 The importance of database design




Defines the database’s expected use
Different approach needed for different types of databases
Avoid redundant data
Poorly designed database generates errors
 leads to bad decisions
 can lead to failure of organization
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1.2 Historical Roots of Database
1.2.1 How modern database evolved from file systems
Managing data with file systems is obsolete
 Understanding file system characteristics makes database design
easier to understand
 Awareness of problems with file systems helps prevent similar
problems in DBMS
 Knowledge of file systems is helpful if you plan to convert an
obsolete file system to a DBMS
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1.3 Files and File Systems
1.3.1 Files / Manual File Systems
 Collection of file folders kept in file cabinet
 Organization within folders based on data’s expected use
(ideally logically related)
 System adequate for small amounts of data with few reporting
requirements
 Finding and using data in growing collections of file folders became
time-consuming and cumbersome
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1.3 Files and File Systems
1.3.2 File Systems / File-Based-Systems
 Conversion from manual to computer system
 A collection of application programs that perform services for the
end-users.
 Could be technically complex, requiring hiring of data processing
(DP) specialists
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1.3 Files and File Systems
1.3.2 File Systems / File-Based-Systems
 A collection of application programs that perform services for the
end-users
 Each programs manages its own data
Data entry
and reports
Sales files
File defination
Sales
application
Sales
application programs
programs
Data entry
and reports
Contracts files
File handling
routines
Sales
File handling
routines
File defination
Sales
application
programs
Contracts
application
programs
Contracts
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1.3 Files and File Systems
1.3.2 File Systems / File-Based-Systems
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1.3 Files and File Systems
1.3.2 File Systems / File-Based-Systems
 As number of databases increased, small file system evolved
 Each file used its own application programs
 Each file was owned by individual or department who commissioned
its creation
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1.3 Files and File Systems
1.3.2 File Systems / File-Based-Systems
 As system grew, demand for DP’s programming skills grew
 Additional programmers hired
 DP specialist evolved into DP manager, supervising a DP
department
 Primary activity of department (and DP manager) remained
programming
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1.4 A File System Critique
1.4.1 About Flaws in File System Data Management
 Every task requires extensive programming in a third-generation
language (3GL)
• Programmer must specify task and how it must be done
 Modern databases use fourth-generation languages (4GL)
• Allow users to specify what must be done without specifying how
it is to be done
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1.4 A File System Critique
1.4.1 About Flaws in File System Data Management




Time-consuming, high-level activity
As number of files expands, system administration becomes difficult
Making changes in existing file structure is difficult
File structure changes require modifications in all programs that use
data in that file
 Modifications are likely to produce errors, requiring additional time to
“debug” the program
 Security features hard to program and therefore often omitted
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1.4 A File System Critique
1.4.2 Structural and Data Dependence
 Structural dependence
– Access to a file depends on its structure
 Data dependence
– Changes in the data storage characteristics without affecting the
application program’s ability to access the data
– Logical data format
• How the human being views the data
– Physical data format
• How the computer “sees” the data
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1.4 A File System Critique
1.4.3 Field Definitions and Naming Conventions
Flexible record definition anticipates reporting requirements by breaking
up fields into their component parts
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1.4 A File System Critique
1.4.4 Data Redundancy
 Data redundancy
– same data are stored in many different locations
 Data inconsistency
– Different and conflicting versions of the same data appear in
different places
– Island of Information – scattered data locations
 Errors more likely to occur when complex
 Data redundancy results in data inconsistency
 Errors more likely to occur when complex entries are made in several
different files and/or recur frequently in one or more files
 Data anomalies develop when required changes in redundant data
are not made successfully
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1.4 A File System Critique
1.4.4 Data Redundancy
 Data anomalies
– Abnormality
– Fosters an abnormal condition by forcing field value changes in
many different locations
– Types of anomalies:
• Modification anomalies
– Occur when changes must be made to existing records
• Insertion anomalies
– Occur when entering new records
• Deletion anomalies
– Occur when deleting records
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1.5 Database System
1.5.1 Database System
 Problems inherent in file systems make using a database system
desirable
– File system
• Many separate and unrelated files
– Database
• Logically related data stored in a single logical data repository
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1.5 Database System
1.5.1 Database System
 Database Management System (DBMS)
– A software that enable user to define, create, maintain and control
access to database
– software that interacts with the end user application program and
database.
• manage dB structure
• controls access to data
• contains query languages
 Database
– A shared collection of integrated computer structure designed to
meet various needs of an organization
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1.5 Database System
1.5.1 Database System
 Each program shared same data for different user views
 Data are save in database and managed by DBMS
Database System
File details +
file definitions
Data entry
and reports
DBMS
Database
Salesapplication
application
Sales
programs
programs
Sales
Data entry
and reports
Contracts
application
Sales application
programs
programs
Contracts
33
1.5 Database System
1.5.2: Database System Component
 an organizations of component that define and regulate the
collection, storage, management and use of data within a database
environment.
 components of a database system:
data
hardware
software
procedure
people
bridge
machine components
human components
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1.5 Database System
1.5.2: Database System Component
 Hardware
– Particular hardware depends on org requirements and DBMS
model
– PC, Web Server, Mainframe
 Software
– dB s/w itself
– IBM DB2, Access, MS SQL, Oracle
 Data
– Collections of facts stored in the dB
– Acts as a bridge – combine machine components & human
components
– Operational data and metadada
– System catalog
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1.5 Database System
1.5.2: Database System Component
 Procedure
– Instructions and rules that govern design and use of the system
 Human
– People involve in the system
• System administrator
• Database administrator (DBAs)
• Database designers
• System analysts and programmers
• End users
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1.5 Database System
1.5.3 The Different Between Database and File System
 Database Management Systems (DBMS)
– a software system that enables user to define, create, maintain
and control access to database.
– software that interacts with the end user application program and
database.
• manage dB structure
• controls access to data
• contains query languages
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1.5 Database System
1.5.3 The Different Between Database and File System
File System
Data entry
and reports
Sales files
Database System
File handling
routines
File defination
Sales application programs
Sales application programs
Data entry
and reports
Contracts files
Database
Sales
File details +
file definitions
File handling
routines
DBMS
File defination
Sales application programs
Contracts application programs
Data entry
and reports
Contracts
Database
Sales
Salesapplication
application
programs
programs
Sales
Data entry
and reports
Sales
application
Contracts
application
programs
programs
Contracts
38
1.5 Database System
1.5.3 The Different Between Database and File System
A Database System
A File System
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1.5 Database System
1.5.4 DBMS Functions
 DBMS performs functions that guarantee integrity and consistency
of data
– Data dictionary management
• defines data elements and their relationships
– Data storage management
• stores data and related data entry forms, report definitions, etc.
– Data transformation and presentation
• translates logical requests into commands to physically locate and
retrieve the requested data
– Security management
• enforces user security and data privacy within database
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1.5 Database System
1.5.4 DBMS Functions
– Multi-user access control
• uses sophisticated algorithms to ensure multiple users can access the
database concurrently without compromising the integrity of the database
– Backup and recovery management
• provides backup and data recovery procedures
– Data integrity management
• promotes and enforces integrity rules
– Database access languages and application programming
interfaces
• provide data access through a query language
– Database communication interfaces
• allow database to accept end-user requests via multiple, different network
environments
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1.5 Database Model
1.5.4 Database Model
Hierarchical Database Model
• Represented by a group of records that relates to each
others by a pointer
Network Database Model
• Based on set theory, a set consists a collection of
records
Relational Database Model
• Based on the mathematical concept of relational
Object-Oriented Model
• Based on object oriented concepts
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Summary
Data
raw facts
Information
Database
DBMS
reveal
meaning of
data
shared
collection of
integrated
computer
structure
designed to
meet various
needs of
organization
a software to
implement
and used
database
43
Summary
 Database design defines the database structure.
 A well-designed database facilitates data management and
generates accurate and valuable information.
 A poorly designed database can lead to bad decision making, and
bad decision making can lead to the failure of an organization.
 Databases were preceded by file systems.
 Limitations of file system data management:
–
–
–
–
–
requires extensive programming
system administration complex and difficult
making changes to existing structures is difficult
security features are likely to be inadequate
independent files tend to contain redundant data
 DBMS’s were developed to address file systems’ inherent
weaknesses
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Exercise 1
 What is data redundancy and which characteristics of the file system
can lead to it ?
 Explain the difference between data and information.
 What is the role of a DBMS, and what are its advantages?
Exercise 2
 What is data independence, and why is it important?
 Discuss the different between file based system and database
system.
 What are the main components of a database system environment?
Exercise 3
1. How many records does the file contain, and how many fields are
there per record ?
2. What problem would you encounter if you wanted to produce a
listing by city? How would you solve this problem by altering the file
structure?
3. What data redundancies do you detect, and how could these
redundancies lead to anomalies?