Abstract—In distributed database system, the distributed
deposition and redundancy data brought convenient to fault
recovery, but they make distributed query processing more
complicated at the same time. Query optimization and processing
is one of the key technologies in distributed database system. It
generally uses semi-join operation to improve the time response
performance of query and reduce communication cost. This
paper briefly described the corresponding concepts and
characteristics of distributed database system, summarized the
goals of distributed database query optimization, and analyzed
the query optimization process based on semi-join operation
combined with the practical application. In addition, it
introduced a classical algorithm which is used for multiple
connection and query optimization based on the semi-join query
optimization, the SDD-1 algorithm.
Keywords-distributed database; semi-join operation; query
optimization
I. INTRODUCTION
The distributed database develops on the basis of
centralized database and it is the collection of data which are
related to each other logically and the connection of database
and computer network.
Distribution and redundancy of data increases the price of
the data transmission cost on the Internet, and makes query
processing be more difficult and complex. Then, query
optimization and processing become one of the key factors for
improving query performance in distributed database. Query
optimization and processing adopt reasonable algorithms and
precisely reduce the transmission of information as far as
possible, which increase the response time performance of the
query, and reduce system overhead. The cost is different for
different query processing method, which means that the query
optimization and processing of distributed database become
more and more important.