1. Unit 18 Database Design Extended Diploma in ICT Julie Hodsdon
Normalisation 2
Unit 18 Database Design
Extended Diploma in ICT
Julie Hodsdon

2. Modelling
The ERD is a top down method of modelling the real life business
Normalisation is a bottom up method
Often based on existing system (possibly paper)
Both methods can be used
They may give different results and the designer has to decide which ones to implement

4. Example Spreadsheet

5. ERD

6. Normalisation

7. Purpose of normalisation
Make sure the table
Has a field that uniquely identifies each row (the primary key)
Does not contain duplicate fields
Does not repeat the same type of values
Does not contain fields that belong in other fields

8. Purpose of normalisation
Make sure fields
Represent a characteristic of the table subject
Contain a single value
Are atomic (not multipart)
Are not calculated
Are unique throughout the database
Have an appropriate name

9. How the Tables Look

10. How the Tables Look