2012 | OriginalPaper | Chapter
Foundations for a Fourth Normal Form over SQL-Like Databases
Authors : Flavio Ferrarotti, Sven Hartmann, Henning Köhler, Sebastian Link, Millist W. Vincent
Published in: Conceptual Modelling and Its Theoretical Foundations
Publisher: Springer Berlin Heidelberg
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In the relational model of data the Fourth Normal Form condition guarantees the elimination of data redundancy in terms of functional and multivalued dependencies. For efficient means of data processing the industry standard SQL permits partial data and duplicate rows of data to occur in database systems. Here, the combined class of uniqueness constraints, functional and multivalued dependencies is more expressive than the class of functional and multivalued dependencies itself. Consequently, the Fourth Normal Form condition is not suitable for SQL databases. We characterize the associated implication problem of the combined class in the presence of NOT NULL constraints axiomatically, algorithmically and logically. Based on these results we are able to establish a suitable Fourth Normal Form condition for SQL.