Elementary Key Normal Form

Elementary Key Normal Form (EKNF) is a subtle enhancement on 3NF. By definition, EKNF tables are also in third normal form (3NF). This happens when there is more than one unique composite key and they overlap. Such cases can cause redundant information in the overlapping column(s).

A table is in Elementary Key Normal Form (EKNF), if and only if, all its elementary functional dependencies begin at whole keys or end at elementary key attributes.

For every full nontrivial functional dependency of the form X→Y, either X is a key or Y is (part of) an elementary key.

Example

For an example of a table whose highest normal form is EKNF, see Boyce–Codd normal form § Achievability of BCNF.

See also

Notes and references

    • Joe Celko’s SQL for Smarties: Advanced SQL Programming, Third Edition
    • A New Normal Form for the Design of Relational Database Schemata by CARLO ZANIOLO - Sperry Research Center
    • Information Modeling and Relational Databases By T. A. Halpin, Antony J. Morgan, Tony Morgan
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