Research on the Query Processing of Multi-Source Heterogeneous Database

Due to the difference in heterogeneous data between multi-databases,studies the query preprocessing,query decomposition and query optimization in the process of query,and presents a solution to the middleware architecture multi-databases system.Query preprocessing makes the equivalent revision of the global query and helps query decomposition to improve efficiency.Query decomposition divides the global query into the local queries which can be carried out in some of the multi-databases,and at the same time ensures that the data of the global query is gained,proposes the methods of query decomposition and the optimized algorithm.