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Elementary key normal form

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This is an old revision of this page, as edited by Manohar reddy123123 (talk | contribs) at 05:16, 8 April 2018 (the composite key page link is taking to compound key page, so it is better worded as compound key and link directly takes to the right page, instead of redirection. Also because compound key is composite key, but not reverse, so it is better worded now.). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

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

A table is in EKNF, if and only if, all its elementary functional dependencies begin at whole keys or end at elementary key attributes.

For every full non-trivial functional dependency of the form X→Y, either X is a key or Y is (a 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[1]
  • Information Modeling and Relational Databases By T. A. Halpin, Antony J. Morgan, Tony Morgan
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