What does Third Normal Form mean?

Definitions for Third Normal Form
third nor·mal form

This dictionary definitions page includes all the possible meanings, example usage and translations of the word Third Normal Form.

Wiktionary

  1. third normal formnoun

    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.)

Wikipedia

  1. Third normal form

    Third normal form (3NF) is a database schema design approach for relational databases which uses normalizing principles to reduce the duplication of data, avoid data anomalies, ensure referential integrity, and simplify data management. It was defined in 1971 by Edgar F. Codd, an English computer scientist who invented the relational model for database management. A database relation (e.g. a database table) is said to meet third normal form standards if all the attributes (e.g. database columns) are functionally dependent on solely the primary key. Codd defined this as a relation in second normal form where all non-prime attributes depend only on the candidate keys and do not have a transitive dependency on another key.A hypothetical example of a failure to meet third normal form would be a hospital database having a table of patients which included a column for the telephone number of their doctor. The phone number is dependent on the doctor, rather than the patient, thus would be better stored in a table of doctors. The negative outcome of such a design is that a doctor's number will be duplicated in the database if they have multiple patients, thus increasing both the chance of input error and the cost and risk of updating that number should it change (compared to a third normal form-compliant data model that only stores a doctor's number once on a doctor table). Codd later realized that 3NF did not eliminate all undesirable data anomalies and developed a stronger version to address this in 1974, known as Boyce–Codd normal form.

Wikidata

  1. Third normal form

    The third normal form is a normal form used in database normalization. 3NF was originally defined by E.F. Codd in 1971. Codd's definition states that a table is in 3NF if and only if both of the following conditions hold: ⁕The relation R is in second normal form ⁕Every non-prime attribute of R is non-transitively dependent on every superkey of R. A non-prime attribute of R is an attribute that does not belong to any candidate key of R. A transitive dependency is a functional dependency in which X → Z indirectly, by virtue of X → Y and Y → Z. A 3NF definition that is equivalent to Codd's, but expressed differently, was given by Carlo Zaniolo in 1982. This definition states that a table is in 3NF if and only if, for each of its functional dependencies X → A, at least one of the following conditions holds: ⁕X contains A, or ⁕X is a superkey, or ⁕Every element of A-X, the set difference between A and X, is a prime attribute Zaniolo's definition gives a clear sense of the difference between 3NF and the more stringent Boyce–Codd normal form. BCNF simply eliminates the third alternative.

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Numerology

  1. Chaldean Numerology

    The numerical value of Third Normal Form in Chaldean Numerology is: 5

  2. Pythagorean Numerology

    The numerical value of Third Normal Form in Pythagorean Numerology is: 4

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"Third Normal Form." Definitions.net. STANDS4 LLC, 2024. Web. 29 Mar. 2024. <https://www.definitions.net/definition/Third+Normal+Form>.

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