Database Management LNotes by John Martin

8/3/2019 Database Management LNotes by John Martin

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R. John Martin

Lecturer in IT, Higher College of Technology

Sultanate of Oman


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Data & Information

Data Information

1 Data is collection of factsand figures

Processed form of data is information

2 No conclusions can bedrawn on data.

Used to draw conclusions.

3 Data is raw material forprocessing. It is processed

further.

Info. Can also be further utilized to

produce high quality information.

4 It is not time bound It is time bounded.

E.g. An amount of money withdrawn from an account on

particular day is a data.

This data is further used for preparing balance sheet,

profit-l loss statement etc. when such processing is

done on data, it is called as information.

Soinformation is processed form of data


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Data vs. Information

Data - a collection of facts made up of text,numbers and dates:

Ahmad 35000 7/18/86

Information - the meaning given to data in the wayit is interpreted:

Mr. Ahmad is a sales person whose annual salaryis $35,000 and whose hire date is July 18, 2006.


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What is a Database

Database is an organized collection of inter related

information. It is a collection of persistent data that can be shared

& interrelated. Persistent Data reside on stable storage such as

magnetic disk and available for ever. Interrelated Data stored as separate units can be

connected to provide a whole picture. It contains conventional & non-conventional

information.

Conventional information - facts about persons,things, events etc.,

Non-conventional information - photographs,fingerprints, videos etc.,


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Database is an organized collection of interrelated

information. When we perform some operation on the data and organize

in some meaningful format, it is called as database system.

The software which allows user to create (table creation) and

maintain (insert, delete, change) database is calledDatabase Management System (DBMS).

DBMS MS-Access, ORACLE, Ingres, INFORMIX,

SyBase, PostgreSQL, MS-SQL Server.

MS

BASE

DATA

Database, Database System & DBMS


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1. Data - (Data / Information)

2. Hardware - ( Computer, Secondary StorageDevices, Processor, Input/Output Devices etc.,)

3. Software - Set of programs. (DBMS)

4. Users - (Application Programmers, End-Users, DBA)

Components (Resources) of a Database System


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PROGRAMMER (Application Program)

FILE-BASED SYSTEM DATA BASE SYSTEM

There are two approaches for storing and maintaining

the data on persistent storage.

Database Approaches


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FILE-BASED SYSTEM

Each programmer has their own set of data withouthaving any link to the other.

They are independent systems (stand alone)

Application programs cannot exchange information.


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TEACHERSSTUDENTSAFFAIRSSTUDENTSREGISTRATION

StudentsRegistration

Details

Student Information Attendance Report

Own set of data

No link / sharing

Works independently

Changing is be done separately

EXAMPLE


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Elements of a database:

Database consists of three major elements.

1. Entities 2. Relationships 3. Procedures

Entity an entity can denote a person, place, thing orevent.Example: Employees, Departments, Students, Course, Registration

etc.,

Relationship it represents a link or a relationship betweenthe entities.Example : Employees working in a department, Students registered

for a course.

Procedures - An ordered set of tasks/rule for performingsome action on the database.Example : Teachers assignment, Course Scheduling, Registering

students.


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Business department wants to create a database which will

store information about all the students those who are

studying the department, all the teachers working in the

department, list of courses offered, the information about

the courses allotted for a teacher, students registered for a

particular course, and teacher for a particular course, using

the above information, Students registration, add courseand drop course should be done successfully.

Find the entities, relationships and procedures in thefollowing problem.


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Entities:

StudentsTeachersCoursesDepartment

Relationships:

Course - TeacherStudentCourseTeacher - Department

Add course

EXAMPLE 1 : COLLEGE DATABASE

Drop Course

Registeringstudents


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In a Hypermarket a database is maintained to store the

information about all the products that are available in that

shop, all the employees working, the shopping carts available

and the details of the customers. Whenever any customer

comes to the shop, the customer should collect all the

products he need in a shopping cart, if he needs any help, he

can contact any employee of the shop and finally a bill

should be generated by an employee and stock should be

updated for all the products.

Find the entities, relationships and procedures in thefollowing problem


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Entities:

CustomersProductsEmployeesShopping-cart

Relationships:

Products - CustomerCustomer Shopping CartShopping Cart - Products

Billing

EXAMPLE 2 : HYPERMARKET DATABASE

Stock Updating


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It is a computerized record keeping system.

Its purpose is to maintain information and make thatinformation available to all users anytime they are

required.

The information kept in a database can be anything thatis important to the company or organization.

DATABASE SYSTEM


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In a database system, data kept in the computer will beintegrated and shared by users.

Integrated means that the database can be thought as a

collection of information where repeated data are removedfrom the system.

Shared means that individual pieces of data in a database

can be shared among different users.

DATABASE SYSTEM (Cont..)


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DATABASE SYSTEM

Students PersonalInformation

Students Attendance

Students Result

DATABASE

STUDENTSAFFAIRS

HEAD OF THE DEPT

LECTURES


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College maintains a file named personal information tostore the details of the students such as Student-Id, Student-name, Specialization, Address, School-details, Emergency-contact number.

Apart from personal information, the college is alsomaintaining a separate file named student resultsto storethe results of the results of the students which consists ofStudent-Id, Student-name, Specialization, Result.

A separate file named students attendance is maintained tostore the attendance details of the students which consiststhe student-Id, Student-name, date-of-absent and period.

Apply File-based / Database Approach


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In a Hypermarket a file named Product-file is used to storethe information about all the products like Product-number,Product-name, Unit, Price, Stock.

A separate file named Employee-file is used to maintain the

details of the employees, like Employee-number, Employee-name, Date-of-birth, Emp-Address, Salary.

Another file named Customer-file is used to store thecustomer details such as Customer-no, Customer-Name,

Cust-Address. A file named Sales-file is used to store the sales details such

as Product-no, Product-Name, Customer-no, customer-name, units, price, total-amount.

Apply file-based / Database approach


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Objectives and Need of Database System

To specify information requirements of user.

To provide ad-hoc reports ( which are not required regularly)

To provide a natural and easy way of structuring of data.

To support the processing requirements & any performance

objective.

To design data structure which will remain robust over time.(i.e. new information can be easily added to database)


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Lab Exercise : Ms-Access

Introduction, Working with tables, Table formatting


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1. Redundancy of data can be reduced.

2. Inconsistency can be avoided

3. Data sharing

4. Security restrictions can be applied

5. Integrity can be maintained

6. Data independence

Advantages of database approach


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1. Redundancy of data can be reduced

Here College_Id, Student_name, Specialization is repeated in

PERSONAL INFORMATION, STUDENT RESULT AND STUDENT ATTENDANCE.

That is redundancy (repetition of information)


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2. INCONSISTENCY CAN BE AVOIDED

College-ID Student-Name Specialization Address

1001 SALIM IT MUSANNA

College-ID Student-Name Specialization Result

1001 SALIM ENG PASS

College-ID Student-Name SpecializationAttendance

%

1001 SALIM IT 79

PERSONAL INFORMATION

STUDENTS RESULT

STUDENTS ATTENDENCE

Inconsistency means incorrect information or confusing information.


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3. DATA SHARING


Students AttendanceStudents Result

STUDENTSAFFAIRS

HEAD OF THE DEPT

LECTURES

Data is easily available to all users in database system as it is shared.


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4. SECURITY RESTRICTIONS

DBA - Database Administrators, USERS

Permissions to access, modify or delete data.

DBA creates users and give rights (permissions)to them to access, modify or deletion ofinformation from table.

Data is more secure in database system than filebased system.


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5. DATA INTEGRITY


Students AttendanceStudents Result

STUDENTSAFFAIRS

HEAD OF THE DEPT

LECTURES

Data that we are storing in database must satisfy some

condition is called data integrity.

e.g: age > 0. such conditions are easily given in database.

The user can rely on the data given by the system

because of Security restrictions and elimination of Data

redundancy.


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6. DATA INDEPENDENCE

USERS

APPLICATION PROGRAMS

DATA

Data Structures (Table Design) can be changed withoutchanging the application programs.


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Database + Application Programes =DBMS

DB

Collection of data.AP - Collection of Programs (Software) to maintain database.

DATABASE MANAGEMENT SYSTEM


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Database Operations (Maintenance):

Insert new information

Retrieve existing information

Delete existing information

Modify existing information

Store the information

Distribute the information

Format the information


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Sharing of data and common interface is provided by DBMS.

Less redundancy.

Efficient and easy data access.

Data integrity is maintained. Provides security for data.

Data administration is easy.

Standards can be enforced.

User need not require to know about location of data on

the disk.

Reduced application development time.

Benefits of DBMS


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Use of expensive hardware and software i.e. it is

costly.

Difficult and costly to develop, because it needstrained professionals, persons.

Centralized data. Complete shut down when

subject to failure.

Disadvantages (Drawbacks) of DBMS:


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Database Applications:

Banking: all money transactions

Airlines: reservations, schedules

Universities: registration of students, results of students.

Sales: customers information, products info., purchases info.

Online retailers: order tracking, customized recommendations

Manufacturing: production, inventory, orders, supply chain

Human resources: employee records, salaries, tax deductions

Databases touch all aspects of our lives


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Types of Data Models

Data Model is a design of database. Data model defines how data is organized, stored and

retrieved in database.

It shows data and their relationship.

There are 3 models.

Hierarchical Model

Network Model Relational Model


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1. Hierarchical Model

It is a database management system that link recordstogether like ordered tree.

The Relationship is One-To-Many Relationship is unidirectional

Data is shown by rectangles

Relationship is shown by lines


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ExampleA

B C D

E F G H

Hierarchical Model ( Like Tree structure)

Disadvantages:

1. Slow in processing.

2. Difficulty in getting data.

3. Difficult programs are required to write to get data.

Parent

Childs


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2. Network Model

Used in early days

Data is shown by rectangles

Relationship is shown by lines

It is shown like arbitrarygraph.

The Relationship is a Many-To-Many

Relationship is unidirectional


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Example

A

B

C

D

E

F

G

Network model ( Like graph)

Disadvantages: Slow in processing than relational model.

Difficulty in getting data.

Difficult programs are required to write to get data.


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3. Relational Model

Collection of tables are used to show data and theirrelationship.

Data is stored in 2 dimensional tables.

Table is collection of rows and columns.

In relational database

Rows are called tuples.

Columns are called attributes.


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Example

Stud_id Name Course

1 Ali IT

2 Mohammad ENG

Stud_id Marks Mobile_No

1 78 95746111

2 67 95111111

1 80 95746333

STUDENT STUDENT-MARKS

Relational model using 2 tables

Row/

Tuple

Column/

Attributes

Data and Relationship shown by two tables.

Table name


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Relational Database is a set ofrelations.

Relation is a table with rows, columns and is made up of two partsnamely schema and instance.

Schema specifies name of relation plus name and type of eachcolumn. For example, Student Table

Sid Number

Name Text

Specialization Text

GPA Number

Instance is a table with rows, columns and row data.For example,

Sid Name Specialization

GPA

111 Ali IT 3

222 Muna IT 2.5

333 Huda IT 3.2


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INTEGRITY CONSTRAINTS

Integrity constraints are conditions that must be true for any instance

of a database. A legal instance of a relation is one that satisfies allspecified Integrity constraints. Integrity constraints are specified using

keys.

KEYS

A set of fields is a key. Keys provide one form of integrityconstraints. Keys are a way to associate rows in different

relations.

Super key:column(s) with unique values

Candidate key: a key, although not selected as a primary key, canalso be used to uniquely identify a row or entity.

Null value: special value meaning value unknown or inapplicable


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Sid and {Sid, GPA}are super keys. Chose any one as primary

key, for instance Sid. The other key becomes candidate key.

A primary key is a field (or combination of fields, called a

composite key), which uniquely identifies a row or entity.

For example consider the following student table,

Sid Name Specialization GPA

Primary key:

F i K


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a field in one relation, which refers to a field in another. Foreign

keys are used in relational schema to represent a relationship

between two relations/entities. A foreign key in one relation refersto the primary key field of the related relation/entity.

an attribute/field or combination of attribute in a table whose value

match primary key in another table.

Sid Cid Grade

111 ITSE1100 A

222 ITDB1102 B111 ENGL1100 C+

111 ITSE1101 B+

Enrollment

Sid Name Login GPA

111 Ali T015 3.2

222 Muna T026 3.3

333 Huda T018 3.0

(Sid, Cid) - Primary Key Sid Primary Key

Sid - Foreign key

Student

Foreign Key:


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Each table has column(s) with unique values. That is no two

rows of a table can contain the same value for the primarykey. In addition, no row can contain a null value for any

columns of a primary key.

For example, the primary key Sid is unique in the

following table.

Sid Name Specialization

GPA

111 Ali IT 3.2

222 Huda IT 3

333 Muna ENGG 3.3

444 Muna IT 3.0

Entity integrity: primary keys

R f i l i i f i k


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Ensures valid references among tables

Foreign keys can be null in some cases Foreign keys must match primary key of referenced table.

For example, Sid is foreign key in Enrollment its values matchwith the Student tables Sid.

Sid Cid Grade

111 ITSE1100 A

222 ITDB1102 B

111 ENGL1100 C+

111 ITSE1101 B+

Sid Name Login GPA

111 Ali T015 3.2

222 Muna T026 3.3333 Huda T018 3.0

(Sid, Cid) - Primary Key Sid Primary KeySid - Foreign key

Enrollment Student

Referential integrity: foreign keys


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Data Model

A data model is an overall design of a database.

It shows a data and relationship between them.

It is a conceptual tool to represent the database.

The data model focuses on what data is required and

how it should be organized.


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The design of the database is a step-by-step

procedure. It can be divided into three separate

stages

Conceptual data modeling

Logical schema construction

Physical database design

For small projects the above stages can be handledby one person only, whereas in big projects each

stage can be handled by separate persons.


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Conceptual data

Modeling

Logical SchemaConstruction

Physical Databasedesign

Big Projects


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Physical Database

Logical Schema Construction

Conceptual data Modeling

Small Projects

Ph f D b D i


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Conceptual Data Modeling

Logical Schema Construction

Physical Database Design

Database Requirements

E R Diagram (on papers)

Relational Database Tables (on papers)

Schema and Instances

(Inside computer)

Phases of Database Design

A) C l D M d li


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A) Conceptual Data Modeling

It includes objects ( i.e. documents ) of an interest to

an organization.E.g. Al Musanaa College of Technology.

Personal informationName - Ali Al Balushi

Section - 1

DOB - 04-Dec-1988

Address - Muladha

Hostel - Yes

GPA - 2.67

LevelLevelcode - 101

Leveldesc -Certificate


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B) Logical Schema Construction Based on data provided by conceptual model, the database

structure is designed on paper. This is known as logical schema

construction.Student Table

Field Name Data Type Field Size Format Decimal

StudId Number Long Integer

Name Text 30

Section Number

DOB Date dd-mmm-yyyy

Address Text 40

InHostel Logical

LevelCode Number Integer

CourseCode Number Integer

Field Name DataType Field Size Format Decimal

LevelCode Number

LevelDesc Text

Level Table


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During the logical schema construction, the following can

be determined.

What element of data you will store?

How large each element can be?

What kind of information each element can contain?

What elements may be left blank?

Which elements are considered to be of a fixed range?

Whether and how various tables are linked?


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C) Physical Database Design

It refers to the actual structures created inside the computer.

Based on data structure designed on paper in the logical

schema construction stage, actual structure are created

inside computer.

Computer

Student Table

Level Table

Attendance Table

Course Table

Physical Database Design:


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Physical Database Design:

Student Table Created In Ms-Access (DBMS)


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Conceptual Modeling

This is the first step of database design.

Relevant elements are identified and analyzed. Such asdocuments like daily attendance report, students grading

sheet and objects like teacher, student, library.

To analyze the information, data modeling techniques are

used. Data Modeling techniques are-

A) Entity Relationship Diagram. (ERD)

B) Normalization.

C) Functional Dependency Diagram. (FDD)

Output of the analysis is called Conceptual Data.

A) E tit R l ti hi Di (ERD)


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A) Entity Relationship Diagram (ERD)1976 proposed by Peter Chen

Entity Relationship Diagram is a conceptual data modeling

technique which shows all entities and the relationship

exists between them.

Entity Relationship Diagram is a graphical representation of

a database.

CustID DepositorCustomerAccount

CustName DOB

CustCity

ActNo

Balance

Entity Relationship Diagram


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In Entity Relationship Diagram

Rectangle represents - Entity Set

Diamond represents Relationship Set

Ellipses represents Attributes

Symbols Used to show relationship between the entities

One-to-One (1:1)

One-to-Many (1:M)

Many-to-Many (M:M) -


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The conceptual model is often stated in terms of:

Entities an entity is an object about which information is

collected. This can be person (i.e. student, teacher), place (i.e.

department), things (grade) or events (attendance).

Entity set Group of similar entities.

e.g. all person, all places.

Attributes Attributes are the properties or characteristics of an

entity. e.g. StudId, StudName, DOB, Address.

Entity Occurrence It is an instance of an entity. i.e. set of

values , usually records or tuple.


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Relationship In database relationship must exists between

entities.

Relationships are classified by their degree, connectivity,

cardinality, direction and type

Attribute Domain Each attribute has permitted set of values

called attribute domain. E.g.

Date might be dd-mmm-yyyy thus 10-May-1980 is valid, but

10/05/1980 not valid for domain of attribute date.

If we give condition salary >= 1000 and salary


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Degree of a Relationship

The degree of relationship is the number of entity setsassociated (linked) with the relationship.

Binary relationship- It is an association between two entity sets


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y p y

Ternary Relationship It involves three entity sets.

N-Ary Relationship More than three entity sets are involved inrelationship

Degree =2

Degree =3

Degree =5


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Mapping Cardinality - Mapping cardinality shows how entities of one entity

set associated with another entity set via arelationship set.

One To One (1:1)

One To Many (1:M)

Many To One (M:1)

Many To Many (M:M)


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One-to-One (1:1)At most one instance of entity set A there is only

one instance of entity set B. And at most oneinstance of entity set B there is onlyone instanceof entity set A.

One-one

A B

e.g.

Car CarNumber

Country - CapitalCity

Department - HeadOfDepartment


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One-to-Many (1:M) For oneinstance of entity setA, there are zero, one

or many instances of entity set B.

But for one instance of entity set B there is onlyone instance of entity setA.A B

One-to-Many

e.g.

One Department - Many

Student


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Many-to-One (M:1) For oneinstance of entity set B , there are zero, one

or many instances of entity setA.

But for one instance of entity setAthere is onlyone instance of entity set B.A B

Many-to-One

e.g.

Many Student One Course


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Many-to-Many (M:M) For oneinstance of entity set A , there are zero, one or

many instances of entity set B.

But for one instance of entity set B there is many

instances of entity set A.A B

Many-to-Many

e.g.

Employee Project

Suppliers Part

Author - Book

O M


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One-to-Many

Consider another entity set; Department and Courses. Looking

at figure below we can say that ONE department can offer

MANY courses.

Business Studies

Marketing

Business Ethics

E-Business

M M


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Many-to-Many

Consider another entity set Students and Courses. Looking at

figure below we can say that ONE Student is registered to

MANY courses and Courses has MANY Students.

Ali Marketing

Business Ethics

E-BusinessHaider

Ismail


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Example ER Diagram.

CUSTOMER

ACCOUNT BANK

HAS

HANDLES


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Relationship with linking words/phrases-

Relationships are also sometimes expressed in verbs (action

words).

e.g. Department Head manages Department.

On the other hand Department is managed by Department Head.

A Department Head can manage only ONE department and

department can have only ONE head ( 1:1 relationship)

Department Head DepartmentManages a

Managed by

MR X IT Department

One-to-One


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References:

Course Text BookTitle : Database Design, Application Development and Administration

Author: Michael V.Mannino

ISBN:0-07121489-5

Chapters: 1 , 2 and 5

E-brary BookTitle: Databases A Beginner's Guide

Author: Oppel, Andy

ISBM:9780071608473

Chapters: 1,7

Database Management LNotes by John Martin

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