Null Values in Relational Databases and Sure Information Answers

  • Hans-Joachim Klein 
Conference paper
Part of the Lecture Notes in Computer Science book series (LNCS, volume 2582)


Null values are ubiquitous in database applications. There is, however, no common agreement upon how to deal with null values, neither in practice nor in theory. In this paper, the null value problem is revisited with special emphasis on answers representing sure information with respect to possible world semantics. The focus is on the unknown and the no information interpretation of null values. A new semantics for the no information interpretation of nulls is proposed taking into account a problem arising in connection with the closed world assumption. Results are applied to the query language SQL.


Relational Database Relational Algebra Query Evaluation Query Formulation Query Semantic 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2003

Authors and Affiliations

  • Hans-Joachim Klein 
    • 1
  1. 1.Institut für Informatik und PraktMathematik Universität KielKielGermany

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