[单选题][A] All in all [B] In addition [C] In case [D] After all
[单选题]A. in generalB. on averageC. by contrastD. at length
[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)A.A→CB.A→DC.C→BD.B→D
设数据结构B=(D, R),其中D=( a, b, c, d, e, f )R=( (a, B), (b, C), (c, D), (d, e), (e, f)
[单选题]给定关系模式R(U,F),U={A,B,C,D,E,F},F={B→F,D→A,A→E, AE→B},那么属性A的闭包为(62),R的候选关键字为(63)。A.ADEB.ABEC.ABCED.ABEF
关系R和S如下图所示,试计算R÷S中有几个元组[1]。 R A B C D a b c d a b e f a b h k b d e f S C D c d
m A B C A B 2 m 2 m ( c ) ( d ) q = 10 kN / m a F 9 A C B A C D B F 0 : 2 m 0.4
[单选题]设有关系模式R(A,B,C,D,E,F),其函数依赖集为F={B→D,C→B,CE→F,B→A}。则R最高属于( )。A.1NFB.2NFC.3NFD.BCNF
[试题](c) Prepare brief notes for the proposed meeting with Charles and Jane. Clearly identify the further informationyou would need in order to advise them more fully and suggest appropriate personal financial planningprotection products, in respect of bot
[单选题]给定关系模式R(U,F),U={A,B,C,D,E},F={B→A,D→A,A→E,AC→B},其候选关键字为(40),则分解ρ={R1(ABCE),R2(CD)}满足(41)。A.ABDB.ADEC.ACDD.CD