Synonyms
SPJRU-algebra; SPCU-algebra
Definition
Positive relational algebra is the fragment of relational algebra which excludes the difference operator. Relational algebra queries are expressions defining mappings from database instances of an input database schema to an output relation. In particular a positive relational algebra query over a database schema Ï„ is one of the following expressions, each one with an associated set of attributes:
A constant relation over a set of attributes U is a positive relational algebra query with associated set of attributes U.
If R(U) is a relation schema in Ï„, the relation symbol R is a positive relational algebra query with associated set of attributes U.
If Q and Q′ are positive relational algebra queries with sets of attributes U and U′, respectively, the following are positive relational algebra queries:
The selection σA=B (Q) or σA=c (Q), with set of attributes U, where A and B are attributes in U, and c is a constant value
The projection π X...
This is a preview of subscription content, log in via an institution to check access.
Access this chapter
Tax calculation will be finalised at checkout
Purchases are for personal use only
Recommended Reading
Abiteboul S, Hull R, Vianu V. Foundations of databases. Reading: Addison-Wesley; 1995.
Author 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
Sirangelo, C. (2018). Positive Relational Algebra. 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_1251
Download citation
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1251
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