This presentation discusses the relationship between schema and entity-relationship (E-R) diagrams. It defines key E-R diagram symbols like entities, attributes, and relationships. It then provides examples of how to represent one-to-one, one-to-many, many-to-one, and many-to-many relationships between tables in a relational database through E-R diagrams. Finally, it shows how to design an E-R diagram from a given schema involving bus routes, drivers, schedules, and their relationships.

1. W E L C O M E T O O U R
P R E S E N TAT I O N

2. Our presentation topic is:
Schema relationship to E-R
diagram.

3. Symbol of ER(Entity Relationship) diagram:
Attribute
Multi value
attributes
Relationshi
p
Week
Entity
Identifying relationship
Entity
Derived Attribute

4. Student
Lecturer
Module
Tutors
Studies
ID
CourseName
Relationship of ER diagram

5. Schema Relationship

6. Schema Relationship
ProductionUnit( Serial#, ExactWeight, ProductType,
Productdesc, QualityTest, LotNumber )
Lot(LotNumber, CreateDate, CostOfMaterials)
RawMaterialsUsage(LotNumber, MaterialID, Units)
RawMaterials(MaterialID, Type, UnitCost)
• Entities
Route( number, departure, destination)
Driver( id, name, phone)
Bus( license, capacity)
• Weak entity
Schedule( number, departure-time)
• Relationship
Drives( number, departure-time, id)
Bus-in-use( license, number, departure-time)

7. Database Keys:
Keys are very important part of Relational database. They are used to establish and
identify relation between tables. They also ensure that each record within a table can
be uniquely identified by combination of one or more fields within a table.
Primary Key – A primary key is a column or set of columns in a table that uniquely
identifies tuples (rows) in that table.
Super Key – A super key. is a set of one or more columns (attributes) to
uniquely identify rows in a table

8. Candidate Key – A super key with no redundant attribute is known as
candidate key.
Composite Key – A key that consists of more than one attribute to uniquely
identify rows (also known as records & tuples) in a table is called composite
key.
Foreign Key – Foreign keys are the columns of a table that points to the
primary key of another table. They act as a cross-reference between tables.

9. Many-to-Many1-to-1 1-to Many Many-to-1
Relationship:

10. One-to-one relationship:
To illustrate the one-to-one relationship consider the sample table design and data
below:
Customer-name-table
Id primary key, link to cust_id of customer details table
Email
mobile
Customer-details-table
Id primary key, link to cust_id of customer name table
Height
Weight

11. To illustrate the one-to-many relationship consider the sample table design and data
below:
authors table
author_id primary key
lastname
firstname
books table
book_id primary key
title
author_id foreign key - link to author_id of authors table
Many-to-one relationship:

12. To illustrate the many-to-many relationship consider the sample table design for a bank
below:
customers table
cust_id primary key key
lastname
firstname
products table
Many-to-many relationship:
mapping table
product_id primary key
name
cust_id
product_id

13. Design ER diagram from the given relation
schema. • Entities
 Route( number, departure, destination)
 Driver( id, name, phone)
 Bus( license, capacity)
• Weak entity
 Schedule( number, departure-time)
• Relationship
 Drives( number, departure-time, id)
 Bus-in-use( license, number, departure-time)
Router Driver Bus
Drives
Schedule
Bus-in-line

14. THANK YOU.