Elementary key normal form
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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 FDs begin at whole keys or end at elementary key attributes.
For every full nontrivial FD of the form X→Y, either X is a key or Y is(part of)an elementary key.
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[1]
- Information Modeling and Relational Databases By T. A. Halpin, Antony J. Morgan, Tony Morgan