13. Summary

The purpose of normalisation is to avoid redundant data and to make it easier to maintain a database by only having to update a record in one place only.

Characteristics of normalisation and normal forms are:

Unnormalised form (0NF)

  • Data might be repeated
  • Data might be non-atomic
  • The table might not have a primary key
  • There might be repeating fields i.e. each field does not have a unique name

First normal form (1NF)

  • There are no columns with repeated or similar data
  • Each data item cannot be broken down any further.
  • Each row is unique i.e. it has a primary key
  • Each field has a unique name

Second normal form (2NF)

  • The table must already be in 1NF
  • Non-key attributes must depend on every part of the primary key

Third Normal form (3NF)

  • The table must alreadybe in 2NF
  • There are no non-key attributes that depend on another non-key attribute


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

Click on this link: Method of normalisation


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