在学生选课数据库S_T中，有: 学生表student（sno,sname,ssex,sage,sdept)， 课程表course（cno,cname

A、select student.* , cno, grade from student join sc on student.sno=sc.sno

B、select student.* , sc.* from student , sc where student.sno=sc.sno

C、select student.sno, sname, ssex, sage, sdept , cno, grade from student , sc where student.sno=sc.sno

D、select student.* , cno, grade from student , sc where student.sno=sc.sno

A、select count(cno) from sc

B、select count(sno) from sc

C、select count(*) from sc

D、select count(distinct sno) from sc

学生基本信息：s(S#，SNAME，SEX．AGE)

选课信息：SC(s#，C#，GRADE)

课程信息：C(c#，CNAME．TEAC|-IER)

若要“查询选修了3门以上课陧的学生的学生号”，正确的SQL语句是---。

A．SEI,ECT’S#FROM SC GROI．JP BY S#l"lAVING COtJNT(*)>3

B．SELECT S# FROM SC GROIJP BY S撑WHERE COLINT(*)>3

C．SELECl’S#FROM SC ORDER BY S#HAVING C0UNT(*)>3

D．SELECT.S#FROM SC ORDER BY S#WHERE COUNT(*)>3

A、create view view1 as select sno,avg(grade) from sc group by sno

B、create view view2 as select sno,sname,sdept from student where sdept='CS'

C、create view view3 as select sno,sage+20 from student where ssex='女'

D、create view view4 as select student.sno,sname,sc.sno,cno,grade from sc,student where sc.sno=student.sno and cno='1'

A、create view view4 as select student.sno,sname,sc.sno,cno,grade from sc,student where sc.sno=student.sno and cno='1' 1

B、create view view2 as select sno,sname,sdept from student where sdept='CS' 2

C、create view view3 as select sno,sage+20 from student where ssex='女' 3

D、create view view1 as select sno,avg(grade) from sc group by sno 4

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.1:1,1:n

B.1:n,1:n

C.n:1. ,n :m

D.n:m.n:m

A、删除student表中的记录

B、修改student表中某条记录的sno值

C、向sc表中插入一条记录

D、修改sc表中某条记录的sno值