Synonyms
Equality query; Equality selection
Definition
Consider a relation R whose schema contains some attribute A taking values over a domain D. A membership query retrieves all tuples in R with A = x (x∈D).
Key Points
A membership query effectively checks membership in a set (relation). As such, it can be implemented using either a hash-based index (built on the attribute(s) involved in the query) or a B+-tree. If a hashing scheme is used, each indexed value is placed on an appropriate hash bucket. Then all records that satisfy A = x are located on the bucket responsible for value x. If A is a numeric attribute (and can thus be indexed using an order-preserving access method like a B+-tree), the membership query is a special case of a range query where the range interval [low, high] is reduced to a single value (low = high = x).
Cross-References
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsAuthor information
Authors and Affiliations
Corresponding author
Editor information
Editors and Affiliations
Section Editor information
Rights and permissions
Copyright information
© 2018 Springer Science+Business Media, LLC, part of Springer Nature
About this entry
Cite this entry
Moro, M.M. (2018). Membership Query. 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_754
Download citation
DOI: https://doi.org/10.1007/978-1-4614-8265-9_754
Published:
Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4614-8266-6
Online ISBN: 978-1-4614-8265-9
eBook Packages: Computer ScienceReference Module Computer Science and Engineering