题目内容

已知关系模式R中U=(A,B,C,D,E)，F=B→A,D→A,A→E,AC→B，则关系R的码为______。

ABD
B. ADE
C. ACD
D. CD

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已知关系R如下表所示，可以作为关系R主码的属性组是______。 A B C D 1 2 3 4 1 3 4 5 2 4 5 6 1 4 3 4 1 3 4 7 3 4 5 6

ABC
B. ABD
C. ACD
D. BCD

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Questions 1 to 5 are based on an interview. At the end of the interview, you will be given 10 seconds to answer each of the following 5 questions. Now listen to the interview. According to Edward, in deciding the location of a house, people should consider all the following EXCEPT

A. the type of life they enjoy.
B. the price of the house.
C. the distance between the house and the place of work.
D. the school their children can attend.

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在关系模式R(S,SN,D)和K(D,CN,NM)中，R的主码是S，K的主码是D，则D在R中称为______。

A. 候选码
B. 备用码
C. 超码
D. 外码

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简述经典条件反射的基本规律。

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已知关系模式R中U=(A,B,C,D,E)，F=B→A,D→A,A→E,AC→B，则关系R的码为______。

ABD B. ADE C. ACD D. CD

已知关系R如下表所示，可以作为关系R主码的属性组是______。 A B C D 1 2 3 4 1 3 4 5 2 4 5 6 1 4 3 4 1 3 4 7 3 4 5 6

Questions 1 to 5 are based on an interview. At the end of the interview, you will be given 10 seconds to answer each of the following 5 questions. Now listen to the interview. According to Edward, in deciding the location of a house, people should consider all the following EXCEPT

在关系模式R(S,SN,D)和K(D,CN,NM)中，R的主码是S，K的主码是D，则D在R中称为______。

简述经典条件反射的基本规律。

ABD
B. ADE
C. ACD
D. CD