1.Intro to Database management System

1. 1
Definitions
 Database: An Organized collection of logically related
data, usually designed to meet the information needs of
multiple users in an organization
 Data: stored representations of meaningful objects and
events
– Structured: numbers, text, dates
– Unstructured: images, video, documents
 Information: data processed to increase knowledge in the
person using the data
 Metadata: data that describes the properties and context of
user data

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Figure 1-1a Data in context
Context helps users understand data

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Figure 1-1b Summarized data
Graphical displays turn data into useful
information that managers can use for
decision making and interpretation

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Descriptions of the properties or characteristics of the
data, including data types, field sizes, allowable
values, and data context

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Types of data
Structured data
includes numbers, text, dates.
Numeric data (numbers), this type of data consists numeric
digits from 0-9. It may either be positive or negative.
Alphabetic data (text), this type of data consists of
alphabetic letters from A-Z,(a-z), blank space e.g “Ali shah’,
“hayat” etc.
Alphanumeric data (dates), it consists digits (0-9), letters
(a-z, A-Z) and all special characters (*,+,@,&,#….)

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Types of data
 Unstructured data
Includes images, audio, videos
Images data consists charts, pictures, paintings.
Audio data , that type of data includes music(audio), speech
or any type of sound.
Video data, collection of full motion images played at high
speed. And used to display actions and movements.

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Data Vs Information
 Data unprocessed raw
facts
 Data is meaningless
 Data is the input of
computer
 Data is extensive in its
volume
 Data is used rarely
 Data is independent
 Data is not functional in
decision making
 Information is processed
form of data
 Information is meaningful
 Information is the output
of computer
 Information is short in
volume
 Information is frequently
used
 Information is dependent
on data
 Information is functional
in decision making

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Entity & Its types
Entity
“An entity is a person, place, object, event or concept in the
user envirment about which the organization wishes to
maintain data”
Example-1; a library system may contain data about different
entities like BOOK and MEMBER
Example-2; a college system may include entities like
STUDENT, TEACHER, CLASS etc.

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Entity & Its types
Some Examples of Entities
Person : employee, Student, Player, Doctor, Patient
Place : Country, City, Store
Object : Vehicle, Toy, Furniture, Building
Event : Sale, Admission, Registration
Concept : Programming, Account, Course
The following symbol used for an entity in ERD.

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Entity & Its types
Each entity in ERD is given a name, since name represent
a collection of items (called attributes)
The entity name is always a singular
We represent the name of entity is capital letters
In ERD the entity name is placed inside a box
(entity symbol) representing the entity type. i.e
STUDENT entity may have the attributes
S_Name, F_name, Address, Class, DOB etc
STUDENT

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Entity & Its types
Entity Type: “A collection of entities that share common
properties or charactistics”
OR
“A set of entities with same attributes is called entity type”
We use capital letters for the names of entity type(s)
An entity type is described just once (using metadata) in a
database.
For example

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Entity & Its types
STUDENT_ID
S_NAME
F_NAME
ADDRESS
DEPARTMENT_NAME
CLASS
BIRTHDATE
INT(4)
CHAR(30)
CHAR(30)
CHAR(40)
CHAR(30)
CHAR(25)
DATE
Entity type:
STUDENT

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Entity & Its types
Entity Instance: “A single occurrence of an entity
type”
OR
“A member of an entity type is known as an entity
instance”
Example:
Two instances of STUDENT (Entity Type)
See example on next page

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Entity & Its types
 Instance 1st
Instance 2nd
01 02
Ali Jan
M Shah Zain
Peshawar Islamabad
IBMS IBMS
Bs(IT) Bs(IT)
July 13,1990 Sep 03, 1991

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Entity & Its types
Many instances ( hundred or thousands) of that
entity type (STUDENT) may be represented by
data stored in the database.

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Entity & Its types
STRONG ENTITY VS WEAK ENTITY TYPES
Strong Entity Type:
“An entity type that exist independently of other entity types”
 Most of the basic entity types to identify in an organization
are classified as strong entity types.
 Instances of a strong entity type always have a unique
charactistics (called identifier) that is an attribute or
combination of attributes that uniquely distinguish each
occurrence of that entity.

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 To represent strong entity in ER Diagram, the
following symbol is used
 Weak Entity Type: “an entity type whose
existence depends on some other entity type”
Entity & Its types

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Entity & Its types
 A weak entity type has no business meaning in the
ER Diagram without the entity on which it
depends.
 The below symbol is used for weak entity type.
 Identifying Owner:” the entity type on which the
weak entity type depends”

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Entity & Its types
 A weak entity type does not have its own
identifier, Generally on an ERD a weak entity type
has an attribute that serves as a partial identifier.
 Identifying Relationship: “ the relationship b/w a
weak entity type and its owner(identifying
owner)”
 Example (next page)

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Entity & Its types
EMPLOYEE
E_ID
E_Name
DEPENDENT
Dependent_name
(first_name,
middle_name,
last_name)
DOB
Example of weak entity type and its identifying
relationship

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Entity & Its types
 In above Fig EMPLOYEE is a strong entity type,
with identifier Employee_ID.
 DEPENDENT is a weak entity type as indicated
by double line rectangle.
 EMPLOYEE (Strong entity type) is the owner of
DEPENDENT (weak entity type)
 “Has” shows the identifying relationship(double
lined diamond symbol).

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Entity & Its types
 The attribute ‘Dependent_Name’ serves as a
partial identifier.
 We use double underline to show a partial
identifier.
Identifier: “An attribute or combination of attribute
that uniquely distinguish individual instance of an
entity type”

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Entity & Its types
 The above Fig ,can be represented in more simple form as
Strong entity Identifying relationship Weak entity

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Attributes & its types
 Attribute – “property or characteristic of an
entity type that is of interest to the
organization”
 Each entity type has a set of attributes
associated with it.
 In Entity Relationship Diagram(ERD) we
represent an attribute with sign of ellipse.
Attribute Symbol in
ERD

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 Following are the some entity types and
their associated attributes
I. STUDENT
[ Student_ID, Student_Name, Home_Address,
Phone_Number]
II. EMPLOYEE
[Employee_ID, Employee_Name,
Designation, Department].
Attributes & its types

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Attributes & its types
 In naming attributes, we use an initial
capital letter and other are in lower
case.
 We represent an attribute(in ERD) by
placing its name in an
ELLIPS(symbol) with a line
connecting it to its associated entity.
e.g (next page)

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Attributes & its types
STUDENT
Student_ID Student_Name Home_Address
Phone_Number

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Attributes & its types
 Types of Attributes:
-Simple Attribute
-Composite Attribute
-Single valued Attribute
-Multi-Valued Attribute
-Derived Attribute
-Stored Attribute

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Attributes & its types
-Simple Attribute: “An attribute that can not
be subdivided into smaller component is
known as simple attribute”
Fig shows
STUDENT entity
and their
attributes(simple
attributes)

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Attributes & its types
- -Composite Attribute: “An attribute that can
be divided into smaller components”
An attribute broken
into component parts
Example-1

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Attributes & its types
Example-2
CUSTOMER entity type with
composite
attribute(Customer_Address)

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Attributes & its types
Single-valued Vs Multi-valued Attribute:
Single-valued attribute: “An attribute that may
contain single value”
e.g. Age of a person is a single-value attribute, also
gender is the example of single-value attribute.
Multi-valued attribute: “An attribute that may
contain two or more values”
 Multi-valued attribute is represented by double-
line oval.

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Attributes & its types
Employee entity type
with multi-valued
attribute(Skill)
Multivalued:
an employee can have
more than one skill

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Attributes & its types
Derived Attribute: “an attribute whose value can be
calculated from other related attribute”
The following fig show s the derived attribute
Derived
from date employed and current date
Multivalued:
an employee can have
more than one skill

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Attributes & its types
Stored Attribute: “An attribute that is stored in a
database is called stored attribute”
Attribute Domain: “A set of possible values for an
attribute is known as attribute domain”
The domain may consist of range of a values or
some discrete values.
e.g. the domain for GPA can be from 0-4, similarly
the domain for ‘Gender’ attribute can be either
‘Male’ or ‘Female’.