Exam-style question
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Explain why databases are normalised and describe how normalisation to third normal form can improve the handling of data. Use an example involving repeated information.
Model answer
What a good answer should say
- Databases are normalised to organise data into suitable relations and reduce unnecessary duplication.
- For example, if a customer relation stores the same customer address on every order, changing the address requires several records to be updated.
- If one record is missed, inconsistent data can result.
- Repeated data can also cause insertion and deletion problems.
Explanation
Why this works
The answer should connect normalisation with reducing redundancy and avoiding update, insertion or deletion anomalies. It should also explain the 3NF condition: no non-key attribute depends on another non-key attribute, after the relation has reached second normal form.
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