F有内部冲突满足P_2且无α环模式分解的研究

Reserch of Schema Decomposition Problem of Meeting P_2 and without α-Cycle of Inside Conlict in Functional Dependency Set F

在数据库模式的无α环分解中,当数据模式R〈W,F〉的FD集F有内部冲突时,无论F是否存在广义左、右部冲突均不存在满足保持FD、无损连接、BCNF和无α环的分解。在某些实际应用中的分解只满足部分条件就够了,在分析F有内部冲突时最小归并依赖集D的特性,给出了归并依赖集满足的条件∑1和∑2,在此基础上,讨论给出了满足P2(保持FD、BCNF)且无α环分解的充要条件和算法,对算法的正确性、可终止性进行了证明,并对算法的时间复杂度给出了分析。

In the decomposition of the database, schema withoutα-cycle, when the FD set F of the database schema R （W, F） has inside conflicts, No matter,whether or not there exist generalized left-hand side conflicts or generalized right-hand side conflicts in FD set F, it is not contented of scheme decomposition of dependency preserving and lossless nough ina lot practical application.By analyzing the property and characteristics the minimum merge dependency set of the FD that exist the inside conflicts, the minimum merge dependency set of the FD need suffice the conditions ∑1 or ∑2. On this basis, across discussion give the necessary and sufficient condition and the scheme decomposition of P2 （dependency preserving and BCNF） and without α-cycle.The decomposition algorithm the decompositions and the proof for its termination and correction are also given.