[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"$fENpLraegKkjVoFLx60fLgcvtegekGiDA6PLSZn6ajis":3},{"answer":4,"createTime":5,"id":6,"options":7,"origin":12,"question":19,"related":20,"source":31,"type":32},[],"2024-05-27 14:31:18",138921385,[8,9,10,11],"必要条件","充分条件","既不充分也不必要条件","充分必要条件",{"count":13,"courseId":14,"courseImg":15,"courseName":16,"workId":17,"workName":18},30,"c0b894dbadf578cbd3eb276427574cc8","https:\u002F\u002Ftihai-oss-cloud.itihey.com\u002Fimg\u002Fb8c613cfff21227b91ae92e05557b243.jpg","数据库系统原理","3fade25286454a02aabb796bcbbc540e","","在关系模式R(U,F)中,R中任何非主属性对候选键完全函数依赖是R∈3NF的( )",[21,33,43,53,63,73,82,91,100,103],{"answer":22,"createTime":23,"id":24,"options":25,"question":30,"source":31,"type":32},[],"2024-04-21 19:55:52",138921377,[26,27,28,29],"3NF","1NF","BCNF","2NF","关系模式R(U)属于1NF,如果它的每一个候选码都是单属性码,那么它至少是( )","v1",0,{"answer":34,"createTime":35,"id":36,"options":37,"question":42,"source":31,"type":32},[],"2024-04-17 23:34:42",138921378,[38,39,40,41],"R中已经 不存在插入与删除异常","R 肯定属于 BCNF","R 仍可能存在一定的插入与删除异常","A和B 都是","当关系模式R(A, B,C,D)已经属于3NF,下面说法正确的是( )",{"answer":44,"createTime":45,"id":46,"options":47,"question":52,"source":31,"type":32},[],"2024-06-11 01:21:03",138921379,[48,49,50,51],"若 Y → Z 成立,则 X → Z","若 WY → Z 成立,则 XW → Z","若 Z⊆U 成立,则 X → YZ","若 X → Z 成立,则 X → YZ","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 ,则以下函数依赖不可能推出的一组是( )",{"answer":54,"createTime":55,"id":56,"options":57,"question":62,"source":31,"type":32},[],"2024-04-17 23:36:47",138921380,[58,59,60,61],"{A2,A3,A4,A6}","{A2,A3,A4,A1}","{A2,A3,A4,A5,A1,A6}","{A2,A3,A4,A5}","已知关系R(A1,A2,A3,A4,A5,A6),函数依赖集F为{ (A2,A3)→A4,A3→A6,(A2,A5)→A1 }, 问(A2,A3)关于F的属性闭包为( )",{"answer":64,"createTime":65,"id":66,"options":67,"question":72,"source":31,"type":32},[],"2024-05-03 01:12:46",138921381,[68,69,70,71],"{ B→A,B→E,D→F,C→F,D→E,B→C,B→D,D→G }","{ B→A,B→E,DC→F,D→E,B→C,B→D,D→G }","{ B→A,B→E,D→E,B→C,B→D,D→G }","{ BC→A,BC→E,DC→E,DC→F,DG→E,B→C,B→D,D→G }","已知关系R(A,B,C,D,E,F,G),函数依赖集F为{ BC→AE,DC→EF,DG→E,B→CD,D→G },问:F的最小覆盖为( )",{"answer":74,"createTime":45,"id":75,"options":76,"question":81,"source":31,"type":32},[],138921382,[77,78,79,80],"ADG→E, AG→E","CD→B,AC→B,CDG→F,FE→CB","F→B,FA→D,A→EF","D→B,G→E","已知关系R(A,B,C,D,E,F,G),函数依赖集F为{ ADG→EF,CD→F,F→B,A→D },问:能从F中推导出的函数依赖是( )",{"answer":83,"createTime":65,"id":84,"options":85,"question":90,"source":31,"type":32},[],138921383,[86,87,88,89],"满足第2范式但不满足第3范式","不满足第2范式","其他都不对","满足第3范式","对关系模式:学生(学号,姓名,课程号,课程名,成绩),说法正确的是( )",{"answer":92,"createTime":93,"id":94,"options":95,"question":99,"source":31,"type":32},[],"2024-04-17 23:34:43",138921384,[96,97,98,88],"R不满足第2范式","R满足第3范式但不满足Boyce-Codd范式","R满足第2范式但不满足第3范式","已知关系模式R(A,B,C,D),函数依赖集F={ A→C, DA→B }.则关于R,说法正确的是()",{"answer":101,"createTime":5,"id":6,"options":102,"question":19,"source":31,"type":32},[],[8,9,10,11],{"answer":104,"createTime":65,"id":105,"options":106,"question":111,"source":31,"type":32},[],138921386,[107,108,109,110],"(T,R),3NF","(S,C),1NF","(T,S),2NF","(T,P),3NF","设有关系模式W(C,P,S,G,T,R),其中各属性的含义是:C课程,P教师,S学生,G成绩,T时间,R教室,根据定义有如下数据依赖集 D={ C→P,(S,C)→G,(T,R)→C,(T,P)→R,(T,S)→R}.关系模式W的一个候选键是_____,W的规范化程度最高达到_____"]