Optimization of Multiple Queries in Relational Database Systems
Junichi Miyao, Kazuyuki Tominaga, Tohru Kikuno, Noriyoshi Yoshida · Systems and Computers in Japan · 1988
Abstract Recently, relational database systems which allow concurrent executions have been developed on mainframes and minicomputers. In such a system, optimization of multiple queries can be performed as an extension of optimization of a single query. By unifying the common operations in the multiple queries, the computation time or the number of disk page fetches can be reduced. In this paper, the optimization of the join operations is considered, since the join operation is the most time‐consuming one in the relational database. A problem (problem JM) is formulated to minimize the number of disk page fetches by unifying the common join operations in multiple queries. The number of page fetches depends on the realization method of a single join operation. In this paper, it is assumed that the join operation follows the nested loops method [4]. This paper proposes a heuristic algorithm for problem JM, and the effectiveness of the method is evaluated by a simulation experiment.