Query Optimization Research Of Database And Its Application

Query optimization is an important technique for designing and implementing database system. It is a crucial factor that affects the capability of database. At present,this technique is successfully applied in all commercial databases.The great success of relational database and SQL mainly benefits from the development of query optimization technology. Searching an optimized executive strategy for every complex query is the key of success for database development. In database field, it is still an N-P problem. In the process of query, ineffective SQL, shortage of statistics and incorrect join order are all the reasons for lowering the query rate. Based on the statistics dictionary and the model, the value-based query optimization is to rewrite the ineffective SQL and select the best join order for multi-tables.This paper takes Criminal Interrogation assistance decision support system as research background. This system applies computer technology in the criminal interrogation entire process, including information management, process track, and summaries of the massive cases experience .This paper puts forward an idea of using genetic algorihtm and simulated annealing algorithm into query optimization .This algorihtm takes syntax tree as a chromosome and its posterorder search result is a code. After population which is made up with chromosome complete its select,cross and variation,we will cite simulated annealing mechanism.Thus the population is be optimized much more.At the same time,the population keeps its diversity and reducing response time of the customer.According to the factual problem of query efficiency in Criminal Interrogation assistance decision support system , this paper analyzes detailedly the concretely executive process of SQL statement reference to the characteristic of database query. Criminal Interrogation assistance decision support system adopts rule-based optimation,so we collect statistics general picture,and analyze relation and index of the database.There are several schemes, such as "automating statistics management for query optimizers", "rewriting the SQL statement".