摘要： 针对关系表达式难以进行无限制一到多数据转换的问题，通过关系代数的扩展表达一到多数据转换，采用递归查询和表函数实现无限制一到多数据转换，在每个输入元组上产生一个或者多个输出元组。递归查询通过创建初始结果，递归获取结果集，并返回最终结果集；表函数声明变量集合，使用过程体和游标循环访问表，迭代输出元组。实验分析不同参数影响因素下有限制和无限制转换的不同方法，结果表明扩展方法能够改善系统性能。

关键词: 关系数据库, 数据转换, 结构化查询语言, 递归查询, 表函数

Abstract: Since relational expressions are difficult to execute one-to-many data transformation, the paper expresses one-to-many transformation by extending relational algebra, the recursive query and the table function should be employed to realize unbounded one-to-many transformation for producing one or several output tuples over every input tuples. Recursive queries create original results to obtain result sets by recursion and return final result sets. Table functions declare variable sets and employ a procedure body and cursor to access tables, iterative output tuples. Experiment analyzes different bounded and unbounded data transformations under different reference influencing factor. The results show the extension method improves performance observably.

Key words: relational database, data transformation, Structure Query Language(SQL), recursive query, table function

中图分类号: 

• TP311