Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Secondary Index

  • Yannis Manolopoulos
  • Yannis Theodoridis
  • Vassilis J. Tsotras
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_758

Synonyms

Non-clustering index

Definition

A tree-based index is called a secondary index if the order which it maintains on the search-key values is not the same as the order of the file which it indexes. For example, consider a relation R with some numeric attribute A taking values over an (ordered) domain D. Assume that relation R is not physically stored on the values of attribute A (i.e., relation R is either stored as a heap – an unordered file, or is ordered on another attribute). Furthermore, assume that a tree-based index (e.g., B+ -tree) has been created on attribute A. Then this index is secondary.

Key Points

Tree-based indices are built on numeric attributes and maintain an order among the indexed search-key values. They are further categorized by whether their search-key ordering is the same with the file’s physical order (if any). Note that a file may or may not be ordered. Ordered is a file whose records are stored in pages according to the order of the values of an...

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Recommended Reading

  1. 1.
    Elmasri RA, Shamkant NB. Fundamentals of database systems. 5th ed. Reading: Addisson-Wesley; 2007.zbMATHGoogle Scholar
  2. 2.
    Manolopoulos TY, Tsotras Y, Vassilis J. Advanced database indexing. Dordecht: Kluwer; 1999.zbMATHGoogle Scholar
  3. 3.
    Ramakrishnan R, Gehrke J. Database management systems. 3rd ed. New York: McGraw-Hill; 2003.zbMATHGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  • Yannis Manolopoulos
    • 1
  • Yannis Theodoridis
    • 2
  • Vassilis J. Tsotras
    • 3
  1. 1.Aristotle University of ThessalonikiThessalonikiGreece
  2. 2.University of PiraeusPiraeusGreece
  3. 3.University of California-RiversideRiversideUSA

Section editors and affiliations

  • Vassilis J. Tsotras
    • 1
  1. 1.University of California-RiversideRiversideUSA