设U为所有属性, X、Y、Z为属性集, Z = U - X - Y, 下列关于多值依赖的叙述中,哪些是正确?
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
查看答案
正确答案: BC 答案分析:无
包含此试题的试卷:
相关的试题
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立
A.若X→→Y,则X→Y
B.若X→Y,则X→→Y
C.若X→→Y,则X→→Z
D.若X→→Y,且Y"Y 则X→→Y'
E.设XYWU,若X→→Y在R (W)上成立, 则X→→Y在R (U)上成立