Er Diagram

3.1Entity Relationship Diagram For library Management System

mId

address

phone

Member

name

has

checkout_date

return_day

occupation

borrows

isbn

Section

name

Phone

f_name

m_name

l_name

1

N

1

N

N

bday

sid

age

duration

1

1

N

nic

grants

Price

author

title

address

name

Name

post

phone

Granter

Book

phone

supplies

Publisher

T-03

T-03

d_charge

address

pid

Notes

3.2 Entity

It is basic object of ER model. The ER diagram shows Entities of library

a section, a member, a book, a granter, a publisher

Entity set

It is a collection of entity

Section, Member, Book, Granter, Publisher

3.3 Attributes

Each entity type has an associated set of properties Called attributes which describe the entity.

Simple attribute

Each entity has a single atomic value

Examples

* Section has section id, name and phone number

* Member has member id, address, telephone, occupation

* Book has call number, title, author ,price

* publisher has publisher id, name, address ,phone number

* Granter has national identify card number ,name, address, phone

Composite Attributes

Composite attribute can be divided into smaller sub parts

Example

* Member name is composite attribute. Name can be divided into first name, middle name, last name

Stored Verses Derived Attribute

When two or more attributes are related one can be derived from the other

Example

* Member age :derived attribute

* Date of birth : Store Attribute

Key Attributes-Key Attribute consist primary key

3.4 Relationship types

Relationship types have certain constraints.

Cardinality Ratio

It specific the number of relationship instances that an entity can participate in

Relationships Types are

1:1 (One to One)

1: N (One to Many)

N: 1(Many to One)

M: N (Many to Many)

One- To –Many Relationships (1: N)

* One Section has many books but one book should...