The best materialized views set was gained by the cost calculation model which was designed using maximum matching method of minimizing effective and in order of query benefit per unit maintenance-cost.

Study on join query processing schemes in a mobile computing environment;

Correct use of outer join query technology can not only reduce the data flow on the network,but also improve the efficiency of system.

So the key of query optimization is optimization of multi-join query.

Because it is the foundation of obtaining Deep Web information that searching the query interface of domain WDB(Web Database) automatically, form discovery method based on SE(Search Engine) and the other is to judge whether the form is query interface.

The information can only be accessed by the query interfaces provided by Web database.

As the amount of information on the Web increases rapidly,much Web information has been rapidly deepened by myriad searchable databases online,where data are hidden behind query interfaces.

Parallel multi-join query optimization algorithm based on PC clusters;

Distribution of processors in parallel multi-join query based on PC clusters

Aiming at the issues of complicated multi-join query in the distributed architecture of disaster data management system,this thesis systemically introduces the principles and characteristics of particle swarm optimization(PSO) algorithm,and analyzes the effectiveness of applying PSO to solve the multi-join query optimization problem.