SQL差分

SQL DIFFERENCE

研究定义在变化中的数据库上的查询。一个查询是一个函数,以数据库表为自变量,也以数据库表作函数值。SQL差分研究自变量变化对查询结果的影响,推导出法则以精确推断因自变量的变化而查询结果应该发生的变化,从而产生了查询差分的概念。对构成SQL查询的各种成份如投影、选择、联接、外联接、二元集合运算等分别研究了各自的差分生成规则,也研究了这些成份相互复合所产生的查询的差分构成方法,从而使所得出的方法几乎复盖了当前使用的大部分查询语句。以此为目的,为SQL查询设计了一套完善的代数符号以使对SQL查询进行代数推导成为可能,并据此发现了SQL系统中的许多鲜为人知的代数性质,有助于为SQL构造完整的理论基础以取代关系代数。

In this paper we studied the queries which are defined on dynamic database.Each query is a function,the database tables are both the arguments and the function values.The ＂SQL Difference＂ is to study how the variation of arguments affects query result,and to deduce principles to precisely infer the deserved changes of a query result incurred by the changes of the argument,on this way we produced a new concept of ＂Query Difference＂.In the paper we studied the generation rules of query differences on various components of SQL queries respectively,such as projection,selection,join,out-join and binary set operations,etc.as well as studied the composition of difference of the queries derived from the mutual compositing of those components.As a result,the solution provided in this paper almost covers a great part of the query syntaxes that are currently in use.To achieve above objective,in this paper a set of complete algebra symbols are designed for SQL query,so that the algebra reasoning on SQL querying becomes possible.During the course,we discovered many rarely known algebraic properties in SQL system.These will help us to build a complete theoretical base for SQL to supersede the relational algebra.