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Normalisation

Normalisation Home

What its about

Theory

Introduction

1. Introduction

normal forms

2. Normal Forms

first normal form

3. First Normal Form

first normal form

4. 1NF example 1

1NF

5. 1NF example 2

second normal form

6. Second Normal Form

2NF

7. 2NF database

2NF

8. 2NF continued

third normal form

9. Third Normal Form

3NF

10. 3NF examples

benefits of normalisation

11. Benefits of normalisation

problems with normalisation

12. Problems of normalisation

summary

7. Forming a 2NF database

Going on with the concert table

CONCERT

Venue	Artist	Attendance	Profit	Style
Wembley	Girls Aloud	53000	12334	Girl band
NEC	Leona Lewis	45000	66433	Female soloist
NEC	Girls Aloud	76090	53789	Girl band

This table needs to be split so that non-dependent attributes are removed and only stored once.

In this case a 'style' table is formed that has Artist as the simple primary key

CONCERT

Venue	Artist	Attendance	Profit
Wembley	Girls Aloud	53000	12334
NEC	Leona Lewis	45000	66433
NEC	Girls Aloud	76090	53789

STYLE

Artist	Style
Girls Aloud	Girl band
Leona Lewis	Female soloist

Now the rule for 2NF is being met by both tables - every non-key attribute is depending on the complete primary key. There is no redundant data.

challenge see if you can find out one extra fact on this topic that we haven't already told you

Click on this link: Compound primary keys