设有关系模式 SC( Sno, Sname, Sex, Birthday, Cno, Cname, Grade, Tno, Tname)满足函数 依赖集: {Sno→Sname, Sno→Sex, Sno→Birthday, Cno→Cname, (Sno, Cno)→Grade, Tno→ Tname}.SC 的主码和属性集( Sno, Tno)的闭包分别是
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
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正确答案: C 答案分析:无
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A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)
A.( Sno,Tno)和 {Cno,Cname,Grade,Tno,Tname}
B.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Cno}
C.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday, Tno, Tname}
D.( Sno, Cno, Tno)和 {Sno, Sname, Sex, Birthday)