A.ρ={R1(W19,R2(XZ)}B.ρ={r1(WZ),R2(XY)C.ρ={R1(WXY),R2(XZ)}D.ρ={R1(WX),R2(YZ)}
A.ρ={R1(W19,R2(XZ)}
B.ρ={r1(WZ),R2(XY)
C.ρ={R1(WXY),R2(XZ)}
D.ρ={R1(WX),R2(YZ)}
A.ρ={R1(W19,R2(XZ)}
B.ρ={r1(WZ),R2(XY)
C.ρ={R1(WXY),R2(XZ)}
D.ρ={R1(WX),R2(YZ)}
A.ρ{R1(WY),R2(XZ)}
B.ρ{R1(WZ),R2(XY)}
C.ρ={R1(WXY),R2(XZ)}
D.ρ={R1(WX),R2(YZ)}
● 关系模式R(U,F),其中U={W,X,Y,Z},F={WX→Y,W→X,X→Z,Y→W }。关系模式R的候选键是__(7)__,__(8)__是无损连接并保持函数依赖的分解。
(7)A.W和Y B.WY C.WX D.WZ
(8)A.ρ={ R1 (WY),R2 (XZ)} B.ρ={ R1 (WZ),R2 (XY)}
C.ρ={ R1 (WXY),R2 (XZ)} D.ρ={ R1 (WX),R2 (YZ) }
A.p={R1(WY),R2(XZ)}
B.p={R1(WZ),R2(XY)}
C.p={R1(WXY),R2(XZ)}
D.p={R1(WX),R2(YZ)}
A.rho;={R1(WY),R2(XZ)}
B.ρ={R1(WZ),R2(XY)}
C.ρ={R1(WXY),R2(XZ)}
D.ρ={R1(WX),R2(YZ)}
A.ρ={R1(AC),R2(ED),R3(B)}
B.ρ={R1(AC),R2(E),R3(DB)}
C.ρ={R1(AC),R2(ED),R3(AB)}
D.ρ={R1(ABC),R2(ED),R3(ACE)}
为了保护您的账号安全,请在“简答题”公众号进行验证,点击“官网服务”-“账号验证”后输入验证码“”完成验证,验证成功后方可继续查看答案!