The Problem of Incomplete Information in Relational Databases

Gösta Grahne

ISBN 10: 3540549196 / ISBN 13: 9783540549192

Published by Springer, Springer, 1991

About this Item

Druck auf Anfrage Neuware - Printed after ordering - In a relational database the information is recorded as rowsin tables. However, in many practical situations theavailable information is incomplete and the values for somecolumns are missing. Yet few existing database managementsystems allow the user to enter null values in the database.This monograph analyses the problems raised by allowing nullvalues in relational databases. The analysis coverssemantical, syntactical, and computational aspects.Algorithms for query evaluation, dependency enforcement andupdates in the presence of null values are also given.The analysis of the computational complexity of thealgorithms suggests that from a practical point of view thedatabase should be stored as Horn tables, which aregeneralizations of ordinary relations, allowing null valuesand Horn clause-like restrictions on these null values. Horntables efficiently support a large class of queriesdependencies and updates.

Seller Inventory # 9783540549192

Bibliographic Details

• Title: The Problem of Incomplete Information in Relational Databases
• Publisher: Springer, Springer
• Publication Date: 1991
• Language: English
• ISBN 10: 3540549196
• ISBN 13: 9783540549192
• Binding: Taschenbuch
• Condition: Neu
• Dimensions: 235W x 155H x 10D millimeters 235 millimeters width by 155 millimeters height by 10 millimeters depth
• Weight: 271 grams

About this title

Synopsis

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.