Database Management Systems - sabraz · 2016-03-01 · Database Management Systems Introduction to...

HNDIT 1105

Database Management Systems

Introduction to the course and Lesson 01: Introduction to DBMS

By

S. Sabraz Nawaz

M.Sc. In IS (SLIIT), PGD in IS (SLIIT), BBA (Hons.) Spl. in IS (SEUSL),

MIEEE, MAIS

Senior Lecturer in MIT

Department of Management and IT, SEUSL

Module Aims & Objectives

• Develop fundamental skills required in planning, organizing,

and storage retrieval of information in computer systems and

skills required for managing / administrating small and mid-

range database systems.

HNDIT 1105, DBMS By: S.Sabraz Nawaz

Learning Outcomes

• At the end of the module the student will be able to:

o Describe the fundamental concepts in databases and data processing

o Analyze and systematically represent relationships in data records and perform data modeling Create, populate and manage relational databases in desktop and server environments

o Use query languages to populate, update and retrieve data from databases

o An introduction to data processing and databases Database management systems Data analysis and Data modeling (ER diagrams and conceptual modeling)

o Relational models and normalizations

o Creating databases using GUI tools Query Languages (Standard Query language)

o Introduction to database security


Outline Syllabus

1. Introduction to DBMS.

2. Database model & Schema

3. Database Design ER model

4. Structure Query Language

5. Table normalization

6. Security concepts & introducing advanced database concepts


Assessment Weight

Type Activity Weighting

Continuous Assessment Class assignments, Group activity, Team based activity and tutorials

50%

End of semester Examination

Structured exam paper 50%


Resources: Equipment, Tools

and Materials• Equipment, Tools and Materials Computer lab with Internet

access, desktop database (such as MS Access or compatible)

Server with a SQL database (MSSQL Server or MySQL

Server) and management tools


Prescribed Text

[1]. Ramez Elmasri and Shamkant B. Navathe, Fundamentals of

Database Systems, (6th Ed.), Addison-Wesley

[2]. Balter, Teach yourself Microsoft SQL Server 2005 Express in

24 Hours, Pearson Educatio


Introduction


Introduction

• A database management system (DBMS) is a collection of programs that enables users to create and maintain a database.

• The DBMS is a general-purpose software system that facilitates the processes of defining, constructing, manipulating, and sharingdatabases among various users and applications.

• Defining a database involves specifying the data types, structures, and constraints of the data to be stored in the database.

• The database definition or descriptive information is also stored by the DBMS in the form of a database catalog or dictionary; it is called meta-data. Constructing the database is the process of storing the data on some storage medium that is controlled by the DBMS.

• Manipulating a database includes functions such as querying the database to retrieve specific data, updating the database to reflect changes in the miniworld (aspect of the real world), and generating reports from the data. Sharing a database allows multiple users and programs to access the database simultaneously.


Introducing the Database

• What is a database? A database is a collection of related data

(University Database, Credit Card Processing Systems, Airline

Reservation Systems, Banking System, etc.)

• A database is a shared, integrated computer structure that

stores a collection of: End-user data, that is, raw facts of

interest to the end user.

• Efficient data management typically requires the use of a

computer database.

• Metadata, or data about data, through which the end-user data

are integrated and managed.


DBMS: Role and Advantages

• The DBMS serves as the intermediary between the user and

the database. The database structure itself is stored as a

collection of files, and the only way to access the data in those

files is through the DBMS.


DBMS: Role


DBMS: Role…

• The DBMS receives all application requests and translates

them into the complex operations required to fulfill those

requests. The DBMS hides much of the database’s internal

complexity from the application programs and users.

• The application program might be written by a programmer

using a programming language such as Visual Basic.NET,

Java, or C#, or it might be created through a DBMS utility

program.


Types of Databases

• A DBMS can support many different types of databases.

Databases can be classified according to the number of users,

the database location(s), and the expected type and extent of

use.


Types of Databases: Number of

Users • A single-user database supports only one user at a time. In

other words, if user A is using the database, users B and C must wait until user A is done. A single-user database that runs on a personal computer is called a desktop database.

• A multiuser database supports multiple users at the same time. When the multiuser database supports a relatively small number of users (usually fewer than 50) or a specific department within an organization, it is called a workgroup database.

• When the database is used by the entire organization and supports many users (more than 50, usually hundreds) across many departments, the database is known as an enterprise database.


Types of Databases: Location

• A database that supports data located at a single site is

called a centralized database.

• A database that supports data distributed across

several different sites is called a distributed

database.


Types of Databases: Time and

Usage• Based on how DBMS are used and on the time sensitivity of

the information gathered from them:

o Operational Database (Transactional or production

database)

o Data warehouse



Usage Operational Database• Transactions such as product or service sales, payments, and

supply purchases reflect critical day-to-day operations. Such

transactions must be recorded accurately and immediately

• A database that is designed primarily to support a company’s

day-to-day operations is classified as an operational database

(sometimes referred to as a transactional or production

database).



Usage data warehouse • A data warehouse focuses primarily on storing data used to

generate information required to make tactical or strategic decisions. Such decisions typically require extensive “data massaging” (data manipulation) to extract information to formulate pricing decisions, sales forecasts, market positioning, and so on.

• Most decision support data are based on data obtained from operational databases over time and stored in data warehouses. Additionally, the data warehouse can store data derived from many sources. To make it easier to retrieve such data, the data warehouse structure is quite different from that of an operational or transactional database.


Example of a database:

University DB

• University database maintaining information

concerning:

o Students

o Courses

oGrades

o and …


An example of a database that stores students and their grades of followed courses

STUDENT Name StudentNumber Class Major

Smith 17 1 CS

Brown 8 2 CS

COURSE CourseName CourseNumber CreditHouse Department

Intro to Computer Science CS 1310 4 CS

Data Structures CS 3320 4 CS

Discrete Mathematics MATH 2410 3 MATH

Database CS 3380 3 CS

GRADE_REPORT StudentNumber Sectionaldentifier Grade

17 112 B

17 119 C

8 85 A

8 92 A

8 102 B

8 135 A


Example: University DB (cont…)

• It shows the database structure and a few sample data.

• It is organized as five files.

o The STUDENT file – data on each student,

o The COURSE file – data on each course,

o The GRADE_REPORT file – data on grades that students

receive in the various sections they have completed


Activity 1

• Why would you choose a database system instead of simply

storing data in flat files (operating system files)? When would

it make sense not to use a database system?


Organizing Data in a Traditional File

Environment

THE DATA HIERARCHYA computer system organizes data

in a hierarchy that starts with the bit, which represents either a 0 or a

1. Bits can be grouped to form a byte to represent one character,

number, or symbol. Bytes can be grouped to form a field, and related

fields can be grouped to form a record. Related records can be

collected to form a file, and related files can be organized into a

database.

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TRADITIONAL FILE PROCESSING

The use of a

traditional approach to

file processing

encourages each

functional area in a

corporation to develop

specialized

applications. Each

application requires a

unique data file that is

likely to be a subset of

the master file. These

subsets of the master

file lead to data

redundancy and

inconsistency,

processing inflexibility,

and wasted storage

resources.

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Problems with the Traditional

File Environment• Problems with the traditional file environment (files maintained

separately by different departments)

o Data redundancy:

• Presence of duplicate data in multiple files

o Data inconsistency:

• Same attribute has different values

o Program-data dependence:

• When changes in program requires changes to data accessed by program

o Lack of flexibility: e.g. can’t create ad hoc reports

o Poor security

o Lack of data sharing and availability

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How a DBMS Solves the Problems

of the Traditional File Environment

• If you have just one database that serves the entire organization, you

eliminate the islands of information.

o You reduce the chances of having redundant and inconsistent data because each

entity has only one record.

o You construct the data separate from the programs that will use them.

o The data are available to whoever needs them, in the form that works best for

the task at hand.

o Securing just one database is much easier than controlling access to multiple

databases.

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HUMAN RESOURCES DATABASE WITH

MULTIPLE VIEWS

A single human resources

database provides many

different views of data,

depending on the

information requirements

of the user.

Illustrated here are two

possible views, one of

interest to a benefits

specialist and one of

interest to a member of the

company’s payroll

department.

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Need for a DBMS

Traditional File System provided by the Operating System is

insufficient to meet the requirements of enterprise applications

Scenario:

A company has a large collection (500 GB) of data on database.

This data is accessed concurrently by several employees.

Questions about the data must be answered quickly, changes

made to the data by different users must be applied

consistently, and access to certain parts of the data must be

restricted.


When NOT to use a DBMS

• High initial investment (DBMS is an expensive software package)

• Applications use small amounts of data

• Lack of resources (disk space, memory, etc.) to support a database

• Single-user applications

• Overhead for flexible querying, security, concurrent access & crash recovery is not required


Advantages of using DBMSs

HNDIT 1105, DBMS

By: S.Sabraz Nawaz

DBMS: Advantages

• Having a DBMS between the end user’s applications and the

database offers some important advantages.

o First, the DBMS enables the data in the database to be shared among

multiple applications or users.

o Second, the DBMS integrates the many different users’ views of the

data into a single all-encompassing data repository.


DBMS: Advantages - Improved

data sharing• The DBMS helps create an environment in which end users

have better access to more and better-managed data. Such

access makes it possible for end users to respond quickly to

changes in their environment

• Concurrent accesses are scheduled by DBMS: users can think

of the data as being accessed by one user at a time



data security• The more users access the data, the greater the risks of data

security breaches.

• Corporations invest considerable amounts of time, effort, and

money to ensure that corporate data are used properly.

• A DBMS provides a framework for better enforcement of data

privacy and security policies.


DBMS: Advantages - Better

data integration• Wider access to well-managed data promotes an integrated

view of the organization’s operations and a clearer view of the

big picture.

• It becomes much easier to see how actions in one segment of

the company affect other segments.


DBMS: Advantages -

Minimized data inconsistency• Data inconsistency exists when different versions of the same

data appear in different places.

• The probability of data inconsistency is greatly reduced in a

properly designed database.



data access• The DBMS makes it possible to produce quick answers to ad

hoc queries.

• From a database perspective, a query is a specific request

issued to the DBMS for data manipulation—for example, to

read or update the data.

• Simply put, a query is a question, and an ad hoc query is an

unpremeditated question. The DBMS sends back an answer

(called the query result set) to the application.

• Example?



decision making• Better-managed data and improved data access make it

possible to generate better-quality information, on which better

decisions are based. The quality of the information generated

depends on the quality of the underlying data.

• Data quality is a comprehensive approach to promoting the

accuracy, validity, and timeliness of the data. While the DBMS

does not guarantee data quality, it provides a framework to

facilitate data quality initiatives.


DBMS: Advantages - Increased

end-user productivity• The availability of data, combined with the tools that

transform data into usable information, empowers end users to

make quick, informed decisions that can make the difference

between success and failure in the global economy.


DBMS: Advantages- Reduced

Application Development Time

• DBMS supports many functions common to applications that

access the database

• These applications are likely to be more robust than

applications developed from scratch because many important

tasks are handled by DBMS instead of being implemented by

the application

• Note: The advantages of using a DBMS are not limited to the

few just listed. In fact, you will discover many more

advantages as you learn more about the technical details of

databases and their proper design.


Describing & Storing Data in a

DBMS• The user of a DBMS is ultimately concerned with some real-

world enterprise, and the data to be stored describes various aspects of this enterprise. For example, there are students, faculty, and courses in a university, and the data in a university database describes these entities and their relationships.

• A data model is a collection of high-level data description constructs used to model the application domain. It hides the low-level storage details.

• Most commercial database systems are based on the relational data model

• It is easier to use a semantic data model to model an application domain. A well-known semantic data model is the Entity Relationship (ER) Model


Describing & Storing Data in a

DBMS (cont.…)• In relational data model, the main construct is a relation.

• A relation has fields that belong to it which contain the name & data type of each field

• A description of data in terms of a data model is called the schema.

o Every relation has a schema, which describes the name of the relation, name of each attribute (field or column), and the type of each column.

o e.g. Students(sid: string, name: string, login: string,

age: integer, gpa: real)


An example instance of the

Students relation


SID Name Login Age GPA

53666 SaNa [email protected] 36 3.7

53668 Kumar [email protected] 34 3.2

53670 Sanath [email protected] 44 3.8

Activity 2

• Describe the following data models1. Hierarchical model

2. Network model

3. Object oriented model

4. Object relational model


Levels of Abstraction in a

DBMS• To illustrate the meaning of data abstraction, consider the example of automotive

design.

• A car designer begins by drawing the concept of the car that is to be produced. Next,

engineers design the details that help transfer the basic concept into a structure that can

be produced. Finally, the engineering drawings are translated into production

specifications to be used on the factory floor.

• As you can see, the process of producing the car begins at a high level of abstraction

and proceeds to an ever-increasing level of detail. The factory floor process cannot

proceed unless the engineering details are properly specified, and the engineering

details cannot exist without the basic conceptual framework created by the designer.



DBMS



DBMS

• DBMS is described at four levels of abstraction:

o External Model

o Conceptual Model

o Internal Model

o Physical Model


Levels of Abstraction in a DBMS:

External Model

• The external model is the end users’ view of the data environment. The term end users refers to people who use the application programs to manipulate the data and generate information. End users usually operate in an environment in which an application has a specific business unit focus.

• Companies are generally divided into several business units, such as sales, finance, and marketing. Each business unit is subject to specific constraints and requirements, and each one uses a data subset of the overall data in the organization.

• Therefore, end users working within those business units view their data subsets as separate from or external to other units within the organization.

• A specific representation of an external view is known as an external schema.

• Each external schema consists of a collection of one or more views and relations from the conceptual schema.



Conceptual Model

• The conceptual model represents a global view of the entire database as

viewed by the entire organization. That is, the conceptual model integrates all

external views (entities, relationships, constraints, and processes) into a single

global view of the data in the enterprise.

• Also known as a conceptual schema, it is the basis for the identification and

high-level description of the main data objects (avoiding any database model–

specific details).

• The most widely used conceptual model is the ER model.

• Generally, the term logical design is used to refer to the task of creating a

conceptual data model that could be implemented in any DBMS.


• Once a specific DBMS has been selected, the internal model maps the conceptual model

to the DBMS.

• The internal model is the representation of the database as “seen” by the DBMS. In

other words, the internal model requires the designer to match the conceptual model’s

characteristics and constraints to those of the selected implementation model.

• An internal schema depicts a specific representation of an internal model, using the

database constructs supported by the chosen database.

• Because the internal model depends on specific database software, it is said to be

software-dependent. Therefore, a change in the DBMS software requires that the

internal model be changed to fit the characteristics and requirements of the

implementation database model.



Internal Model

• The physical model describes the way data are saved on storage media such as disks or tapes. The

physical model requires the definition of both the physical storage devices and the (physical) access

methods required to reach the data within those storage devices, making it both software- and

hardware- dependent.

• The storage structures used are dependent on the software (the DBMS and the operating system) and

on the type of storage devices that the computer can handle.

o Describes storage details

o Summarizes how the relations described in the conceptual schema are actually stored on

secondary storage devices such as disks and tapes

o Decide what file organizations used to store the relations

o Create indexes to speed up data retrieval operations



Physical Model

How does a DBMS do all this?• DBMS is a complex software package and the major components of a

DBMS are shown

HNDIT 1105, DBMS By:

S.Sabraz Nawaz

Activity 3

• Explain the Structure or Architecture of a DBMS (e.g.: explain

how it processes a query).


Queries In A DBMS

• With reference to a fictitious university database

1. What is the name of the student with student ID

SEU/IS/98/MG/16?

2. What is the average salary of lecturers who teach the

course with course ID MIT22033?

3. How many students are enrolled in course MIT22033?

4. Is there any student with a GPA less than 3.0 enrolled in

course CS564?

• These questions involving the data stored in a DBMS are

called queries


Reference:

Ramakrishnan, R., & Gehrke, J. (2003). Database management

systems. Osborne/McGraw-Hill. (Pp. 03– 23)


Database Management Systems - sabraz · 2016-03-01 · Database Management Systems Introduction to...

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