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Everything about Third normal form

Level of database normalization

Third normal form (3NF) is a level of database normalization defined by English computer scientist Edgar F. Codd. A relation is in third normal form if it is in second normal form and also lacks non-key dependencies, meaning that no non-prime attribute is functionally dependent on any other non-prime attribute. In other words, each non-prime attribute must depend solely and non-transitively on each candidate key. William Kent summarised 3NF with the dictum that "a non-key field must provide a fact about the key, the whole key, and nothing but the key". Wikipedia →

🧭 Start here: a 6-step reading path

  1. Read the overview: Third normal formA 5-minute orientation
  2. Skim a recent paper: Synthesizing Third Normal Form Schemata that Minimize Integrity Maintenance and Update Overheads: Parameterizing 3NF by the Numbers of Minimal Keys and Functional DependenciesInfluential work since 2022
  3. Pick up a classic book: Practical mysticismThe most-reprinted book on the subject
  4. Read the landmark paper: Synthesizing third normal form relations from functional dependenciesCited 320 times
  5. Go sideways: Second normal formA closely related topic
  6. Go sideways: Boyce–Codd normal formA closely related topic

📖 Definitions

Noun A stage in the normalization of a relational database in which a database is in second normal form and all non-key attributes are mutually independent (no transient dependencies.)

🗂️ The subject at a glance

  1. Definition of third normal form
  2. Example
  3. "Nothing but the key"
  4. Computation
  5. Considerations for use in reporting environments

🏆 Landmark papers (most cited)

🆕 Influential since 2022

📚 Books worth reading

Ranked by number of editions on Open Library, a rough measure of how lasting a book is.

🔗 Related topics