Kostenko P. Models, method and information technology of external SQL-query optimization under databases structural uncertainty

The thesis is devoted to the solution of current scientific problems - increasing the speed of access to information in information systems that use relational databases in uncertainty of logical and physical database structure by developing methods and information technology for external optimization SQL-queries. Method of automatic external optimizing SQL-queries in conditions of uncertainty of physical and logical structure of the database is developed. This method is based on creation and using of a local model of query execution and allows it to receive fast data accessing by determining an optimal syntactic query structure. Set-theoretic model of information system, which, unlike existing models merges SQL-query structure and output data structure at the cost of onto function, that show internal processes querying execution DBMS tools is developed. This model allows to describe the process of external optimization. Method for creating a local model of the controlled process as a controlling influence equivalent to external disturbances has further development. This method unlike existing, adapted to problems of optimal choice in discrete control systems and to determine the syntactic structure of SQL-query with minimal performance time under uncertainty of physical and logical structure of the database.