在学生选课数据库中有学生表student(sno,sname,ssex,sage,sdept)，课程表course(cno,cname)及学生选课表sc(sno,cno,grade)，其中sno是学号，sname是姓名，ssex是性别，sage是年龄，sdept是系别，cno是课程号，cname是课程名，grade是成绩。查询至少选修了“201815005”同学所选课程的学生的姓名，可以使用如下SQL语句。select snamefrom student swhere sno<;>;‘201815005’ and not exists(select *from sc xwhere x.sno='201815005' and not exists(select *from sc ywhere y.cno=x.cno and y.sno=s.sno ) )

下列查询中,属于相关子查询的有（）。 A: SELECT * FROM student WHERE sno IN (SELECT sno FROM sc WHERE cno='1'); B: SELECT sno, cno FROM SC x WEHRE grade&gt;=(SELECT AVG(grade) FROM SC y WHERE y.sno = x.sno); C: SELECT sname FROM student WHERE EXISTS(SELECT * FROM sc WHERE sno=student.sno AND cno='1'); D: SELECT sname FROM student WHERE NOT EXISTS(SELECT * FROM course WHERE NOT EXISTS(SELECT * FROM sc WHERE sc.sno=student.sno AND sc.cno=course.cno));

以下命令是相关子查询的嵌套查询是： A: SELECT * FROM student WHERE sno IN (SELECT sno FROM sc WHERE cno = '1') B: SELECT * FROM student WHERE EXISTS (SELECT * FROM sc WHERE cno = '1' AND sc.sno = student.sno) C: SELECT sno, cno FROM sc x WHERE grade>(SELECT AVG(grade) FROM sc y WHERE y.sno = x.sno) D: 以上都是

有关系S(SNO, SNAME, SAGE)，C(CNO, CNAME)，SC(SNO, CNO, GRADE)。其中SNO是学生号，SNAME是学生姓名，SAGE是学生年龄， CNO是课程号，CNAME是课程名称，GRADE是成绩。以下（ ）SQL语句可以实现查询选修了'C002'号课程的学生姓名。 A: SELECT SNAME FROM S, SC WHERE S.SNO=SC.SNO AND CNO='C002' B: SELECT SNAME FROM S WHERE SNO IN (SELECT SNO FROM SC WHERE CNO='C002') C: SELECT SNAME FROM S WHERE SNO = (SELECT SNO FROM SC WHERE CNO='C002') D: SELECT SNAME FROM S WHERE SNO NOT IN (SELECT SNO FROM SC WHERE CNO='C002')

查询选修1号课程的学生姓名的sql语句为： select sname from student where sno = (select sno from sc where cno=1);