单选题
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表为学生表，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
WHFRF 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'))
【正确答案】
C
【答案解析】
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