In order to indicate that a particular attribute does not have any data associated with it, the variable-length record format makes use of the null bitmap. In certain peculiar circumstances, a tuple could have the majority or even all of its properties set to the value null. Changing the way in which records are represented may cut the overhead of a null attribute down to a single bit, which is a significant savings of space.

In order to indicate that a particular attribute does not have any data associated with it, the variable-length record format makes use of the null bitmap. In certain peculiar circumstances, a tuple could have the majority or even all of its properties set to the value null. Changing the way in which records are represented may cut the overhead of a null attribute down to a single bit, which is a significant savings of space.

Principles of Information Systems (MindTap Course List)

12th Edition

ISBN:9781285867168

Author:Ralph Stair, George Reynolds

Publisher:Ralph Stair, George Reynolds

Chapter5: Database Systems And Applications

Section: Chapter Questions

Problem 2SAT

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A null bitmap is used in the variable-length record format to indicate that an attribute has no value. In a few odd cases, the majority of a tuple's properties are null. It is possible to minimise the cost of a null attribute to a single bit by modifying the way records are represented.
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