摘要
本文证明:当数据依赖集D由等值生成依赖组成并且数据库模式R关于D有无损连接时,已有的在覆盖型嵌套fd的假设下关于恒时维护模式的识别和省效查询处理的结果仍然适用。我们也将证明,当数据依赖由fd和一个jd组成时,对任何取自单个关系模式的属性集X,现有的计算恒时维护模式的X—完全投影的方法仍然适用。
When only equality generating dependencies (egd's) appear as constraints D and (database) scheme R is lossless with respect to D, the previously known recognition and boundedness results for ctm schemes cover embedding fd's are applicable. It is also shown that, for any attributes X from a single relation scheme of the database, the known method of computing X-total projections can be still used for ctm schemes when fd's plus a single jd are constraints.
出处
《电子学报》
EI
CAS
CSCD
北大核心
1990年第5期60-64,共5页
Acta Electronica Sinica
