Optimization for a Distributed Query

Distributed databases are the outcomes of top notch technology advances, high speed computer networks further facilitated its growth and its suitability in satisfying various businesses needs make it more popular. The major area of proposed work is query optimization in distributed database systems. The objective of query optimization is to execute the query with minimum cost. In order to perform join operation, two sub queries involving data from multiple sites has to be transmitted from one site to other. As data resides at different sites in a distributed database environment, so to acquire a specific type of data, subdivision of a query into its sub-parts (sub-queries) is required and those sub-queries needs to be executed at different data sites. In some cases combination of data from two or more different sites may be required. To attain this goal a join operator is used. But using join is not always advantageous in terms of cost as it may sometimes result in more communication cost in cases when complete relation is not desired for join operation. In such scenario communication cost involved between two sites can be reduced using other forms of joins like inner join. Inner join is also not always useful. So a need of finding the appropriate strategy to decide and assign join operations arises.