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Encyclopedia of Database Systems pp 2798–2799Cite as

Primary Index

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Synonyms

Clustering index; Sparse index

Definition

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. Elmasri R, Navathe SB. Fundamentals of database systems. 5th ed. Boston: Addisson-Wesley; 2007.

    MATH  Google Scholar 

  2. Manolopoulos Y, Theodoridis Y, Tsotras VJ. Advanced database indexing. Dordrecht: Kluwer; 1999.

    MATH  Google Scholar 

  3. Ramakrishnan R, Gehrke J. Database management systems. 3rd ed. New York: McGraw-Hill; 2003.

    MATH  Google Scholar 

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Author information

Authors and Affiliations

  1. Aristotle University of Thessaloniki, Thessaloniki, Greece

    Yannis Manolopoulos

  2. University of Piraeus, Piraeus, Greece

    Yannis Theodoridis

  3. University of California-Riverside, Riverside, CA, USA

    Vassilis J. Tsotras

Authors
  1. Yannis Manolopoulos
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  2. Yannis Theodoridis
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  3. Vassilis J. Tsotras
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Corresponding author

Correspondence to Yannis Manolopoulos .

Editor information

Editors and Affiliations

  1. Georgia Institute of Technology College of Computing, Atlanta, GA, USA

    Ling Liu

  2. University of Waterloo School of Computer Science, Waterloo, ON, Canada

    M. Tamer Özsu

Section Editor information

  1. University of California-Riverside, Riverside, MA, USA

    Vassilis J. Tsotras

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Manolopoulos, Y., Theodoridis, Y., Tsotras, V.J. (2018). Primary Index. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_757

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