【单选题】导游在带团时要通过自己的言行向外国游客宣传中国,这体现了导游服务的( ) 。
【简答题】● 给定关系模式R ( U,F) ,U = {A,B,C,D }, F={A→C,A→D,C→B,B→D},F 中的冗余函数依赖为(1);若将R分解为ρ={AC,CB,BD},则ρ 满足 (2)。 (1)A. C→A B. D→A C. B→C D. D→B (2) A. 不具有无损连接性,而且不保持函数依赖 B. 不具有无损连接性,但保持函数依赖 C. 具有无损连接性,而且保持函数依赖 D. 具...
【单选题】给定关系模式R(U,F),U={A,B,C,D},F={A→C,A→D,C→B,B→D),F中的冗余函数依赖为 (43) ;若将R分解为ρ={AC,CB,BD},则ρ满足 (44) 。 (43)
【单选题】导游在带团时要通过自己的言行向外国游客宣传中国,这体现导游服务的 ( )。
【单选题】Whether work should be placed among the causes of happiness or among the causes of unhappiness may perhaps be regarded as a doubtful question. There is certainly much work which is exceedingly weary a...
A.
Work can keep people busy as if they were poor.
B.
Work is a cause of the greatest delight of life.
C.
Work is very tiresome, especially when too excessive.
D.
Work can at least give relief from boredom.
【单选题】Judicial department,
A.
is the strongest among the three.
B.
is the weakest among the three.
C.
makes public policies.
【单选题】给定关系模式R(U,F),其中U为关系R属性集,F是U上的一组函数依赖,若 X→Y,(42)是错误的,因为该函数依赖不蕴涵在F中。
【单选题】Whether work should be placed among the causes of happiness or among the causes of unhappiness may perhaps be regarded as a doubtful question. There is certainly much work that is exceedingly weary an...
A.
Work is very tiresome, especially when toe excessive.
B.
Work is a cause of the greatest delight of life.
C.
Work can at least give relief from boredom.
D.
Work can keep people busy as if they were poor.
【单选题】Whether work should be placed among the causes of happiness or among the causes of unhappiness may perhaps be regarded as a doubtful question. There is certainly much work that is exceedingly weary an...
A.
Work is very tiresome, especially when too excessive.
B.
Work is a cause of the greatest delight of life.
C.
Work can at least give relief from boredom.
D.
Work can keep people busy as if they were poor.
【简答题】● 给定关系模式R ( U,F) ,U = {A,B,C,D }, F={A→C,A→D,C→B,B→D},F 中的冗余函数依赖为(43);若将R分解为ρ={AC,CB,BD},则ρ 满足 (44)。 (43) A. C→A B. D→A C. B→C D. D→B (44) A. 不具有无损连接性,而且不保持函数依赖 B. 不具有无损连接性,但保持函数依赖 C. 具有无损连接性,而且保持函数依赖...