Encyclopedia of Database Systems

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

Primary Index

  • Yannis ManolopoulosEmail author
  • Yannis Theodoridis
  • Vassilis J. Tsotras
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_757


Clustering index; Sparse index


A tree-based index is called a primary index if its order is the same as the order of the file which it indexes Consider a relation R with some numeric attribute A taking values over an (ordered) domain D. Assume that relation R has been physically stored as an ordered file, following the order of the values of attribute A. Furthermore, assume that a tree-based index (e.g., B +-tree) has been created on attribute A. Then this index is primary.

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 attribute. Obviously, a file can have at most a single such order since it is physically stored once. For example, if the Employee...

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Recommended Reading

  1. 1.
    Elmasri R, Navathe SB. Fundamentals of database systems. 5th ed. Boston: Addisson-Wesley; 2007.zbMATHGoogle Scholar
  2. 2.
    Manolopoulos Y, Theodoridis Y, Tsotras VJ. Advanced database indexing. Dordrecht: 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
    Email author
  • 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