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●Suppose we have the relation schema R(A,B,C,D)with functional dependencies;F{A→B,B→C,C→D,

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●Suppose we have the relation schema R(A，B，C，D)with functional dependencies；F{A→B，B→C，C→D，D→A}，then R(A，B，C，

D．at least is in (73) ．

(73) A．1NF

B．2NF

C．3NF

D．BCNF

参考答案:

D【解析】假如我们有关系模式R(A、B、C、D)，它具有函数依赖F{A→B、B→C、C→D、D→A}，那么R(A、B、C、D)至少是BCNF范式。

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