查询语句SELECT *FROM StudentWHERE Sdept = 'CS'EXCEPTSELECT *FROM StudentWHERE Sage <= 19;可以等价为：（ ）
A. SELECT * FROM Student WHERE Sdept = 'CS' AND Sage > 19;
B. SELECT * FROM Student WHERE Sdept = 'CS' AND Sage <= 19;
C. SELECT * FROM Student WHERE Sdept = 'CS' OR Sage <= 19;
D. SELECT * FROM Student WHERE Sdept = 'CS' OR Sage > 19;
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选择题：在所有学生中查询比计算机系学生平均年龄大的学生姓名，可以使用的查询语句是：
A. SELECT SnameFROM StudentWHERE Sage > (SELECT AVG(Sage)FROM Student);WHERE Sdept = 'CS'
B. SELECT SnameFROM StudentWHERE Sage > AVG(SELECT SageFROM StudentWHERE Sdept = 'CS');
C. SELECT SnameFROM StudentWHERE Sage > (SELECT AVG(Sage)FROM StudentWHERE Sdept = 'CS');
D. SELECT SnameFROM StudentWHERE AVG(Sage) > (SELECT SageFROM StudentWHERE Sdept = 'CS');
查询所有未达60分的选课记录，要求显示出该学生的姓名、该门课程的名称和分数，不正确的查询语句是：（ ）
A. SELECT Student.Sname, Course.Cname, SC.GradeFROM SC, Student, CourseWHERE SC.Sno = Student.SnoAND SC.Cno = Course.CnoAND SC.Grade < 60;B.SELECT Student.Sname, Course.Cname, SC.GradeFROM StudentLEFT JOIN SCON SC.Sno = Student.SnoLEFT JOIN CourseON SC.Cno = Course.CnoWHERE SC.Grade < 60;
B. SELECT Student.Sname, Course.Cname, SC.GradeFROM SCLEFT JOIN StudentON SC.Sno = Student.SnoLEFT JOIN CourseON SC.Cno = Course.CnoWHERE SC.Grade < 60;
C. SELECT Student.Sname, Course.Cname, SC.GradeFROM StudentLEFT JOIN SCON SC.Sno = Student.SnoLEFT JOIN CourseON SC.Cno = Course.CnoWHERE SC.Grade < 60;
D. SELECT Student.Sname, Course.Cname, SC.GradeFROM CourseLEFT JOIN SCON SC.Cno = Course.CnoLEFT JOIN StudentON SC.Sno = Student.SnoAND SC.Grade < 60;
查询所有选修了数学（课程号为2）的学生姓名，不正确的查询语句是：（ ）
A. SELECT Student.SnameFROM Student, SCWHERE Student.Sno = SC.SnoAND SC.Cno = 2;
B. SELECT Student.SnameFROM StudentLEFT JOIN SCON Sno = Student.SnoWHERE SC.Cno = 2;
C. SELECT Student.SnameFROM StudentWHERE Sno In (SELECT SnoFROM SCWHERE Cno = 2);
D. SELECT SnameFROM SCLEFT JOIN StudentON Student.Sno = SC.SnoWHERE SC.Cno = 2;
集合操作可用来连接两个结果集，所有的集合操作语句都可以转换成不含集合操作的单语句查询。
A. 对
B. 错
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