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Normalisation. Ham Ham’s Hammy Club. Introduction. What is normalisation? “a technique for designing relational database tables to minimize duplication of information and, in so doing, to safeguard the database against certain types of logical or structural problems” wikipedia.com.

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normalisation

Normalisation

Ham Ham’s Hammy Club

introduction
Introduction
  • What is normalisation?

“a technique for designing relational database tables to minimize duplication of information and, in so doing, to safeguard the database against certain types of logical or structural problems”

wikipedia.com

ham ham s hammy club customer record
Ham Ham’s Hammy Club – Customer Record

I’m kind of a big deal!

MemberID:

Initial:

Surname:

Title:

Sex:

Postcode:

Tel No:

Hammy Details:

ham ham s hammy club customer record1
Ham Ham’s Hammy Club – Customer Record

I’m kind of a big deal!

MemberID: 0001

Initial: A

Surname: Dolinski

Title: Mr

Sex: Male

Postcode: HA1 HA1

Tel No: 0123456789

Hammy Details:

relationships
Relationships
  • Hamster can have one owner
  • Owners can have many hamsters

Hamster

Owner

relationships1
Relationships
  • A hamster can only be one breed
  • A breed can have many hamsters

Hamster

Breed

relationships2
Relationships

Owner

Hamster

Breed

ham ham s hammy club customer record2
Ham Ham’s Hammy Club – Customer Record

I’m kind of a big deal!

MemberID: 0001

Initial: A

Surname: Dolinski

Title: Mr

Sex: Male

Postcode: HA1 HA1

Tel No: 0123456789

Hammy Details:

We can see we already have issues with repeated data!

example data1
Example Data

Customer information is repeated

example data2
Example Data

Breed information is repeated

normalisation rules
Normalisation Rules
  • 1NF
    • No repeating attributes and primary key of non repeating data must be placed in table of repeating data.
  • 2NF
    • Look for non-key attributes that depend upon all the attributes in the compound primary keys i.e. does the attribute depend on both primary keys?
  • 3NF
    • Look for non-key attributes that depend upon other non-key attributes.
1nf apply rules
1nf – Apply Rules

In some cases, you may need to add a new field to make a compound primary key.

2nf apply rules
2nf – Apply Rules

This fixes the many-to-many problem!

3nf apply rules
3nf – Apply Rules

Here we have a foreign key – a non-primary key that links to a primary key in another table.

remember
Remember!!
  • You don’t actually need to know how to normalise a database. It’s useful to know though because you’ll have a better understanding of it – it’ll also help in coursework!
  • However, you need to know the advantages of doing so and you’ll need to know the rules.