Summary of Normal Forms

 

Summary of Normal Forms

Normal FormTest (Condition)Problem RemovedRemedy (Normalization)
First Normal Form (1NF)
The relation should not contain multivalued attributes or repeating groups. Each field must contain atomic (single) values.

    Repeating     groups and     nested relationsCreate separate relations for multivalued attributes and keep a primary key to link them.

Second Normal Form (2NF)
The relation must be in 1NF, and no non-key attribute should depend on only part of a composite primary key.

    Partial         
   dependency		Decompose the relation into smaller tables so that each non-key attribute depends on the whole primary key.
Third Normal Form (3NF)The relation must be in 2NF, and no non-key attribute should depend on another non-key attribute.    Transitive              dependencySplit the table so that non-key attributes depend only on the primary key.

Simple Way to Remember

1NF

  • No repeating attributes

  • All values must be atomic

👉 Rule: One cell = one value

2NF

  • Must be in 1NF

  • No partial dependency

👉 Rule: Every non-key attribute must depend on the entire primary key.

3NF

  • Must be in 2NF

  • No transitive dependency

👉 Rule: Non-key attributes depend only on the primary key, not on other non-key attributes.

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