1. Entity Relationship Diagram Prepared by: Lobna Morsy
(ERD)
Prepared by: Lobna Morsy
Suppliers
#supplier_code
supplier_name
Products
#product_id
product_name
product_price
Customer_Orders_Products
#order_line_id
quantity
Customer_Orders
# order_id
date_order_placed
discount_rate
Customers
#customer_id
first_name
middle_name
last_name
Customer_Addresses
#address_id
street_address
city
state_province_county
country
Customers_Payment
_Methods
# card_number
date_from
date_to
Product_Types
#product_type_code
product_type_name
Payment_Methods
#payment_
method_code
payment_
method_name
supply
supplied by
belongs to
has
places
placed by
ordered
include
includes
included in
chosen
chooses
belongs to
owns
owned

2. Agenda
Database
Components of ERD
Practice Reading ERDs

3. What is a database?
Database: Central source of data meant to be shared by many users for a variety of applications

4. Components on an ERD Entities (table) Relationships (business rules)
Attributes (column)
Entity Name
verb
Entity Name
#attribute_1
attribute_2
attribute_3

5. Entities
Entity Name
Entity: Something about which someone chooses to collect data (table)
Person
Place
Thing
Event
Unit of time
Customers
Cinemas
Tickets
Purchases
Show
times

6. Relationships
verb
Relationships: Associations between entities (business rules)
Optionality
Mandatory
Optional
verb
One
Many
Cardinality

7. Relationships
verb
Cardinality
One
Many
Optionality
Optional
Mandatory

8. Reading Relationships
Employees
Tasks
belong to
assigned to
entity_name one and only one/many verb may/must entity_name Each
Each entity_name may/must verb one and only one/many entity_name
Each task must belong to one and only one employee
Each employee may be assigned to many tasks

9. Examples of Relationships
Each entity_name may/must verb one and only one/many entity_name
Instructors
Courses
teach
taught by
Employees
Offices
assigned to
assigned for
Suppliers
Products
supply
supplied by

10. Attributes
Entity Name
#attribute_1
attribute_2
attribute_3
Attribute: some characteristics of an entity (column) Primary key: used to uniquely identify a record.
Suppliers
#supplier_code
supplier_name
contact_person
contact_person_phone

11. Customer_Orders_Products
Suppliers
#supplier_code
supplier_name
Products
#product_id
product_name
product_price
Customer_Orders_Products
#order_line_id
quantity
Customer_Orders
# order_id
date_order_placed
discount_rate
Customers
#customer_id
first_name
middle_name
last_name
Customer_Addresses
#address_id
street_address
city
state_province_county
country
Customers_Payment
_Methods
# card_number
date_from
date_to
Product_Types
#product_type_code
product_type_name
Payment_Methods
#payment_
method_code
payment_
method_name
supply
supplied by
belongs to
has
places
placed by
ordered
include
includes
included in
chosen
chooses
belongs to
owns
owned