Data base management system(DBMS), sourav mathur

DATA BASE
MANAGEMENT
SYSTEM (DBMS)

INTRODUCTION
DATABASE SYSTEM :
╺ A database is a set of logically related data that is organised so
that it can easily be retrieved, managed and updated. The
modern database are managed by sophisticated software
known as database management system (DBMS).
╺ The database which uses DBMS for data collection, retrieval and
updating is called database system.
2

3
A database system offers the following to the users :
•an easy way to collect, update and retrieve stored infomation;
•data stability by preventing unnecessary loss of data;
•data protection by preventing unauthorised use of data; and
•ensures data quality in terms of accuracy, availability and usability
.

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1. Improve data sharing by providing a easy and feasible system.
2. Improve data security.
3. Better data integration at one place for better efficiency.
4. Minimized data inconsistency.
5. Improved data access.
6. Improved decision making.
7. Increase end-user productivity.
Advantages of data base management system :

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1. Increased costs
2. Management complexity
3. Maintaining currency
4. Frequent upgrade/replacement cycles

9
FACTORS File System
DEFINATION
A file system is an abstraction to store,
retrieve, manage, and update a set of files,
along with keeping track of the files and also
manage them.
Data Program
Independence
Data definition is typically part of application
program and therefore data and program are
dependent to each other.
Data Sharing
Data is stored in separate files in different
departments of the organization, which
makes data sharing throughout the
organization difficult.
Data
Redundancy
Since separate files are maintained in
different departments for usage requirements,
it leads to duplication or manipulation of data
i.e. data redundancy

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FACTORS File System
Data
Consistency and
Accuracy
In file system, the degree of data
consistency and accuracy is low because of
data redundancy
Data Security
The degree of data security in the file
system is very low
Multiple view of
Data
In traditional file system, creating multiple
views of data is next to impossible
Cost
A low cost approach of database
mangement.

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FACTORS File System
Error Correction
Correcting error in all relevant file is very
difficult and complex
Data Retrieval
Retrieval of stored data is difficult

Advantages of
traditional file
system

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Advantages of Traditional File System
1.Simple to use.
2. Less complex.
3. Minimal investment (Not make the investment in software because it
allows us to transport files from one to another computer).
4. No requirement of the specialist.

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Disadvantages of
file system

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Disadvantages of Traditional File System
1. Data redundancy (Each application has its own data file so, same data may have to be recorded
and stored in many times).
2. Data inconsistency (Due to the same data items that appear in more than one file do not get
updated simultaneously in each and every file).
3. Data dependence (Program and application in the file processing system are data dependent
but, the problem is incompatible with file format).
4. Limited data sharing.
5. The problem with security.
6. Retrieval (retrieval is not easy).
7. Time-consuming.
8. Inefficient to maintain the record of the big firm having a large number of items.
Required Lots of labor work to do.

MODERN APPROACH TO
DATABASE
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DESIGNING A DATABASE
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Database design is a process of producing detailed data model of a database.
It requires a complete knowledge of the business functions for which a data
model has to be designed- A database design is a logical design of base data
structure developed for the purpose Of storing data.
The following steps are taken for designing a database :
1. REALITY.
2. ENTITY RELATIONSHIP DESIGN.
3. RELATION DATA MODEL.
4. NORMALIZATION

1. REALITY
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– Process of designing starts with a real world situation, known
as reality, for which the database is to be designed.
– All aspects of reality must be clearly understood by the
designer.
– E.g.: Database for library, The library will be reality, and one
need to understand all aspects of a library, i.e. the nature of all
transactions that happen in library in reality.

2. ENTITY RELATIONSHIP DESIGN.
19
– After getting complete details of reality (real world
situation), a formal blueprint, with pictorial presentation is
prepared using the concept of ER Model to present the
details of the reality

3. RELATION DATA MODEL
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– Once the blueprint, i.e. ER diagram is ready, it is
transformed into inter related tables.
– To Create tables, the details are divided into major
entities and then each entity becomes a table.
– Relationship between tables are defined to maintain data
integrity.

4. NORMALIZATION
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– This is the process of refining a database design.
– It follows set of rules proposed by Edger F. Codd and
eliminates or reduces data redundancy.
– It makes sure that the tables are structured correctly.
– The database design is analysed for errors and, if needed,
normalization rules are applied

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REALITY
ER- DESIGN
NORMALIZATION
IS THERE A
NEED TO
REFINE ?
FINAL DATABASE DESIGN
NO
YES
FLOW CHART: PROCESS OF DESIGNING A DATABASE

ER-MODEL
╺ BASIC CONCEPTS
23

Entity
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An entity can be a person, place, object, event or concept in the
user environment about which the data is collected. An entity can
be a real-world object, either animate or inanimate, that can be
easily identifiable.
Entity = Database Table
• Represented as a named rectangular shape, which may have
a number of attributes. EMPLOYEE

Attributes
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Entities are represented by means of their named properties, or
characteristics of an entity, is of inetrest to an organization, called attributes.
• Describes the entity in terms of its characteristics such as code, name,
height, weight, etc.
• All attributes have values. For example, a student entity may have name,
class, and age as attributes.
• There exists a domain or range of values that can be assigned to attributes.
For example, a student's name cannot be a numeric value. It has to be
alphabetic. A student's age cannot be negative, etc.

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TYPES OF
ATTRIBUTES
Simple
attribute
Derived
attribute
Single-
value
attribute
Composite
attribute
TYPES
OF
ATTRIBUTES

Simple attribute
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Simple attributes are atomic values, which cannot
be divided further. E.g. A student's phone number is
an atomic value of 10 digits, a gender of employee
can not be subdivided.

Composite attribute
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Composite attributes are made of more than one simple
attribute. For example, a student's complete name may
have first_name and last_name.

Derived attribute
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Derived attributes are the attributes that do
not exist in the physical database, but their
values are derived from other attributes
present in the database. For example,
average_salary in a department should not
be saved directly in the database, instead it
can be derived. For another example, age
can be derived from data_of_birth.
Represented by a dotted oval.

Single-value attribute
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Single-value attributes contain single value. For
example − Social_Security_Number. Represented by
single oval.

Multi-value attribute
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Multi-value attributes may contain more than one values.
For example, a person can have more than one phone
number, email_address, etc. Represented by double
oval.

Key attribute
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Unique, distinguishing characteristic of the entity. The
values of the key attributes are distinct for each individual
entity. For eg.: Unique ID no. of the citizens of a country. It
may consist of a single attribute or multiple attributes in
combination. For eg. Emp_Id is a key attribute as it is a
unique no. in the organization. Represented by an
underlined oval

RELATIONSHIP
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• A relationship represents some association between two or more entities.
• Defines the manner in which the entities interact.
• The association among entities is called a relationship.
• The entities that are enrolled in a relationship are known as participants.
• The relationships are generally given names.
• The degree of relationship is defined by the number of participants in the relationship.
• For example, an employee works_at a department, a student enrolls in a course. Here,
Works_at and Enrolls are called relationships.
• Relationship is represented as a diamond shape containing the name of relationship between
entities.

Relationship Set
35
A set of relationships of similar type is called a relationship
set. Like entities, a relationship too can have attributes.
These attributes are called descriptive attributes.

Relationship Between Entitie
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1. One-to-one
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For every row of entity 1 there is only one row row
corresponding to entity 2. Represented as (1:1). • E.g.:
Two entities “Boy” and “Girl”. Assuming one Boy will
marry only one girl and one girl will marry only one boy ,
the relationship represented between the entities in on-
to-one.
BOY MARY GIRL

2. One-to-Many
40
Relationship is there when, for every row in first table (Entity 1)
There exist zero, one or many rows in the second table (Entity 2).
• Represented by (1:N).
• In ER diagram crowfoot (<) is used to show this relationship, in
which crowfoot represents many rows.
• The one to many relationship is shown by department employee
relationship. One Department can have many employees.
EMPLOYEE DEPLOYED DEPARTMENT

3. Many –to-Many
41
Said to exist, if for every row in the first table (Entity 1) there can be many rows in
the second table (Entity 2), and for every row in the second table, there can be
many rows in the first table.
• Represented by (M:N) •
Eg.: Student studies subject. There can be many students who can study the
subject, whereas there can be many subjects which can be studied by the student.
STUDENTS STUDIES SUBJECTS

DEGREE OF
RELATIONSHIP
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–Unary Relationship
–Binary Relationship
–Ternary Relationship

1. Unary Relationship
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• A relationship between the instances of a single entity type.
• Only a single entity participates.
• Also called recursive relationship.
• A “person” wish to represent “marriages” between persons. It involves a relationship
between one instance of a person entity with another instance of person entity.
• To show such relationship in ER diagram, the entity is connected twice with the diamond
showing the relationship.

2. Binary Relationship
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• The relationship between two entities.
• In the last example if we divide the employees (a single entity) into two
different entities “managers” and “workers”, there exist two entities and the
relationship between them will be a binary relationship.

3. Ternary Relationship
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A ternary relationship is when three entities participate in the relationship.
For Example: The University might need to record which teachers taught
which subjects in which courses. The connectivity of a relationship is its
classification.

Data base management system(DBMS), sourav mathur

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