在分布式查询处理中，要根据不同的优化目的来设计各种查询处理的优化算法。
In Distrabuted query, we should devise the query optimization algorithm according to different optimization purpose.
本文设计和实现了一个分布式的城市电磁环境数据库系统以及系统中的分布式查询处理模块。
This paper designed and realized a distributed database system of the urban electromagnetic environment and the distributed query processor in the system.
在分布式数据库系统中，由于数据的物理分布使得分布式查询处理增加了许多新的复杂性，不同的查询处理策略，其查询处理代价和复杂度是大不一样的。
When adding distributed data into the database system, distributed query process is more difficult and complicated. The cost of query process is different due to different query process tactics.
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