Abstract:
By analyzing the property and characteristics of D( the minimum merge dependency set of F) when D has weak left side conflict or weak left side conflict, the notions of Ps(join-lossless, FD and SNF), condition T are introduced. On this basis, the scheme decomposition is discussed and the result concludes that when D has weak left side conflicts or weak right side conflict or doesn’t meet condition T, the decomposition meeting Ps is α-cyclic, laying the foundation for further investigation of α-acyclic decomposition.
Key words:
Without inside conflict,
Weak left side conflict,
Weak rignt side conflict,
α-acyclic,
Simple normal form
摘要: 通过分析在FD集F的最小归并依赖集D存在弱左部或弱右部冲突时所具有的性质和特征,提出了PS(保持FD,无损连接且满足SNF)、条件T等概念。在此基础上讨论了数据库模式分解为SNF的无α环判定问题,给出了在D有弱左部或弱右部冲突及不满足条件T时满足PS的分解是有α环的结论,为进一步研究无α环的分解奠定了基础。
关键词:
无内部冲突,
弱左部冲突,
弱右部冲突,
无α环,
简单范式
ZHAO Lingqiang; GU Zhaopeng; HAO Zhongxiao;. Deciding Problem of Database Schema Meeting Ps and α-acyclic in Functional Dependency[J]. Computer Engineering, 2007, 33(01): 62-64.
赵龄强;顾照鹏;郝忠孝;. 数据库模式在FD环境下满足PS及无α环判定问题[J]. 计算机工程, 2007, 33(01): 62-64.