Optimizing universal queries in relational databases
Minoru Ito, Tadao Kasami · Systems and Computers in Japan · 1991
Abstract In a relational database system based on the universal relation interface, users do not have to specify access paths when constructing universal queries. Moreover, users cannot control how to evaluate the queries efficiently (though they can construct usual queries, such as relational algebraic expressions, considering their processing costs). Thus, it is important for the system to evaluate given universal queries efficiently. This paper considers the representative instance of a database as a universal relation, and presents an optimization algorithm for evaluating a universal query for computing specified components of the tuples in the universal relation which satisfies a specified condition.