UID:
almahu_9948621253302882
Umfang:
VIII, 164 p.
,
online resource.
Ausgabe:
1st ed. 1991.
ISBN:
9783540465072
Serie:
Lecture Notes in Computer Science, 554
Inhalt:
In a relational database the information is recorded as rows in tables. However, in many practical situations the available information is incomplete and the values for some columns are missing. Yet few existing database management systems allow the user to enter null values in the database. This monograph analyses the problems raised by allowing null values in relational databases. The analysis covers semantical, syntactical, and computational aspects. Algorithms for query evaluation, dependency enforcement and updates in the presence of null values are also given. The analysis of the computational complexity of the algorithms suggests that from a practical point of view the database should be stored as Horn tables, which are generalizations of ordinary relations, allowing null values and Horn clause-like restrictions on these null values. Horn tables efficiently support a large class of queries, dependencies and updates.
Anmerkung:
Relational databases -- Semantic aspects of incomplete information -- Syntactic and algorithmic aspects of incomplete information -- Computational complexity aspects of incomplete information -- Some conclusive aspects.
In:
Springer Nature eBook
Weitere Ausg.:
Printed edition: ISBN 9783662207529
Weitere Ausg.:
Printed edition: ISBN 9783540549192
Sprache:
Englisch
DOI:
10.1007/3-540-54919-6
URL:
https://doi.org/10.1007/3-540-54919-6
