The Research And Realization Of Dualistic Constraint Database Model And Query Optimization

In recent years, along with the considerable amount of research about constraint database theory, the issues about constraints on the database have gradually become a new point and a hot spot. With the constant use of relational databases, it was discovered that there was a kind of constraints,which had very broad range of applications in a variety of practical problems. This constraint could be added to the original database,and also could be added to the query results,here we called it "dualistic relational constraint", dualistic-constraint for short. It gives some dualistic relations between the value fields of the two of attributes on which each record of tables could only fetch the value of these dualistic relations. Of course,it has wide application prospects in numerous fields.This dualistic relational constraint is existent widely, but in the classic relational database theory, all kinds of "dependency" is neither related to this kind of constraint. Therefore, in order to make database that contained a large number of dualistic relational constraints do more efficient and optimized query, insertation, modification, and other operations. We need do seriously study for dualistic relational constraint's related issues,and also need further study to the realization of the dualistic constraint database model and other related operations.So, in this paper it puts forward to bring in the ideas and related theories of dualistic constraint based on the ordinary relational database scheme,and to enlarge the simple RDS to define dualistic-constraint. By the way,we can establish the new preliminary model on which we have expanded the theory of dualistic constraint. On this basis,we continue to discuss its realization of storage structure, and also the realization of DDL, DML manipulation and parts of relational algebra manipulation based on this new model. Thus, on the one hand we have extended modeling capabilities of relational data, and on the other hand, using the norms of dualistic constraint, the mature relational database theories and technologies, we can achieve the dual constraint database system in this paper.The central feature of the constraint database is to make the dual constraint as a permanent data to storage. In the latter part of this paper, we will compare to the realization detail of other constraint database's language in order to expand the function of common database language system. And, accordingly, we will introduce the query implementation process of the new expanding database language. Query optimization is an important technology for the design and implementation of database system, and is also an important factor affecting database system performance. Dualistic constraint relational model has resolved the minimum problem of inequality conjunction query based on the arbitrary domain data in the database. Therefore, in this paper, we bring in the minimum of theory of inequality conjunction query, and in the new expanded model we will show how to achieve the better query optimization.In the end, this paper makes an exposition of the system structure of the new expanded model, and, accordingly it has given the experimental data , diagrams and instructions in order to further demonstrate a new model in the superiority of query optimization. Of course, there are still many questions and related aspects to be furtherly explored in the article,so at the end we point out the directions to work about the related fields in the future.