1. Lesson Objectives Aims You should know about: 1.3.2:
(a) Relational database, flat file, primary key, foreign key, secondary key, entity relationship modelling, normalisation and indexing.

2. Copyright
A lot of material here is referenced from a lecture given at Nottingham University

3. Entities
An entity is an object
Usually, entities convert in to tables in a database
Entities, as tables, have attributes
E.g. the entity “student” will have the attributes “name”, “d.o.b”

4. Entities

5. Attributes
Attributes appear on ER diagrams as ovals
But you don’t need to do them in the exam or on this course
It’s nice to know about them, though, right?

6. Attributes

7. Relationships
Entities have relationships
This is a description of how they are related/connected together.
They are represented by lines with a diamond shape in the middle.
In the exam, the diagram is slightly different…

9. Relationships
There are 3 types of relationship:
One to One
One to Many (or many to one)
Many to Many
These relationships are called “Cardinality”

10. Exam Diagrams
In the exam, the diamond shape will be omitted:

11. Examples

12. Many to many
Many to many relationships are a bad thing
They are difficult to represent in a database
Many to many relationships are not in 3nf

14. Task
Slide 15 – Examine the example and follow through how an ER diagram is produced.
Make notes on identifying Entities, Attributes, relationships etc

15. Review/Success Criteria
You should know:
How to interpret ER symbols
How to draw an ER diagram
How to identify relationships, entities and attributes
How to remove many to many relationships