1.5 Summary: 3NF
- A relation is in 3NF if it contains no repeating groups, no partial
functional dependencies, and no transitive functional dependencies.
- To convert a relation with transitive functional dependencies to 3NF,
remove the attributes involved in the transitive dependency and put them
in a new relation.
- Rule: A relation in 2NF with only one non-key attribute must be in 3NF
- In a normalised relation a non-key field must provide a fact about the
key, the whole key and nothing but the key.
- Relations in 3NF are sufficient for most practical database design
problems. However, 3NF does not guarantee that all anomalies have been removed.