Performance Evaluation and Optimization of Queries in Multi Databases

Modern database systems use a query optimizer to identify query plan to execute declarative SQL queries. Optimization is a mandatory exercise since the difference between the cost of the best plan and a random choice could be in orders of magnitude. The role of query optimizers is especially critical for the decision-support queries featured in data warehousing and data mining applications. For a query on a given database and system configuration, the optimizer's plan choice is primarily a function of the selectivities of the base relations participating in the query. In this chapter, it has been projected towards the cost of sub-query operations on the various sites, as well as the benefits achieved in the range of thirty to forty percent for various sub-operations like selection, projection and join.

Autorentext

Sambit Kumar Mishra is presently working as a Professor (Computer Sc.&Engg.) & Head (R&D) in Gandhi Institute for Education & Technology, Bhubaneswar, Odisha. He is member of Editorial Board of several Journals like, IJDATS ( Inderscience Publishing House), IJAERS, JCSA, AJIS, JECET and member of Professional bodies ,ISTE,CSTA,IAENG,IACSIT,CSI