基于空值环境下扩展关系模型的查询处理研究

Research on Inquiry Processing Based on ExtendedRelation Model Under Null Value Circumstances

由于空值的出现，使数据库更新操作更趋复杂。为适应更新要求，建立了扩展关系模型。本文正是基于这种模型进行对查询处理的讨论，给出了相应的查询策略及实现过程。

The update operation of database tends to become more complex, because null valueappears.To meet the needs of updating, the extended relation model is founded. In this paper, theupdate processing is discussed based on this model, and the corresponding inquiry strategy and implementation procedure are given.