将Student表中的Sno属性定义为主码，下面空格处应填写（）。 Create Table Student （Sno char（9) , Sname char（20) Not Null, Sex Char（2) )

A.REVOKE UPDATE ON TABLE Student(Sno) FROM ZHANG;

B.REVOKE UPDATE ON TABLE Student(Sno) FROM ALL;

C.REVOKE UPDATE(Sno) ON Student FROM ZHANG;

D.REVOKE UPDATE(Sno) ON Student  FROM  PUBLIC;

A.On

B.In

C.For

D.As

A.属性b

B.属性c

C.属性bc

D.属性d

A.b

B.c

C.bc

D.d

A.SELECT DISTINCT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno;

B.SELECT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno;

C.SELECT DISTINCT Sno, DISTINCT Sname FROM Student WHERE Student.Sno IN (SELECT Sno FROM SC);

D.SELECT Sno, Sname FROM Student WHERE Student.Sno IN (SELECT DISTINCT Sno FROM SC);

A.当候选码多于一个时，选择一个作为主码

B.主码既可以是单个属性，也可以是属性组

C.全码是指由一个关系模式中所有属性构成的码

D.只有包含在主码中的属性才是主属性

A.(‘1000’, ‘zhang1’, ‘M’, 18)

B.(NULL, ‘zhang3’, 1, 18)

C.(‘1001’, ‘zhang2’, NULL, NULL)

D.(‘1003’, NULL, 1, 18)