问题
单项选择题
对于教学数据库的三个基本表:S(Sno,Sname,Ssex),SC(Sno,Cno,Grade),C(Cno,Cname,Teacher),其中S为学生表,SC为学生选课表,C为课程表,则对于语句:检索至少选修LIU老师所授课课程中一门课程的女生姓名,SQL语句错误的是______。
A.SELECT Sname
FROM S,SC,C
WHERE S.Sno=SC.Sno AND SC.Cno=C.Cno AND Teacher='LIU' AND Ssex='F'
B.SELECT Sname
FROM S WHERE Ssex='F' AND Sno IN
(SELECT Sno
FROM SC
WHERE Cno IN(SELECT Cno FROM C
WHERE Teacher='LIU'))
C.SELECT Sname
FROM S WHERE Ssex='F' AND EXISTS
(SELECT*
FROM SC
WHERE SC.Sno=S.Sno AND EXISTS
(SELECT*
FROM C
WHERE Teacher='LIU'))
D.SELECT Sname
FROM S WHERE Ssex='F' AND EXISTS
(SELECT*
FROM SC
WHERE SC.Sno=S.Sno AND EXISTS
(SELECT*
FROM C
WHERE C.Cno=SC.Cno AND Teacher='LIU'))
答案
参考答案:C
解析: 此题考查SQL语句的正确写法。