On estimating the cardinality of the projection of a database relation
- 1 March 1989
- journal article
- Published by Association for Computing Machinery (ACM) in ACM Transactions on Database Systems
- Vol. 14 (1) , 28-40
- https://doi.org/10.1145/62032.62034
Abstract
We present an analytical formula for estimating the cardinality of the projection on certain attributes of a subset of a relation in a relational database. This formula takes into account a priori knowledge of the semantics of the real-world objects and relationships that the database is intended to represent. Experimental testing of the formula shows that it has an acceptably low percentage error, and that its worst-case error is smaller than the best-known formula. Furthermore, the formula presented here has the advantage that it does not require a scan of the relation.Keywords
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