题中假定学生关系是S(S#,SN.,SEX,AGE),课程关系是C(C#,CNAME,TEACH-ER),学生选课关系是SC(S#,C#,GRADE)。
检索选修课程"C2”的学生中成绩最高的学生的学号,正确的SELECT语句是______。
A.SELECT S# FORM SC
WHERE C#="C2"AND GRADE>=(SELECT GRADE FORM SC
WHERE C#="C2")
B.SELECT S# FORM SC
WHERE C#="C2"AND GRADE IN(SELECT GRADE FORM S
C.
WHERE C#="C2"C) SELECT S# FORM SC
WHERE C#="C2"AND GRADE NOT IN(SELECT GRADE FORM SC
WHERE C#="C2")
D.SELECT S# FORM SC
WHERE C#="C2"AND GRADE>=ALL(SELECT GRADE FORM SC
WHERE C#="C2")