问题
单项选择题
| 设关系模式SCG (S#, C#, grade)中S#为学生学号，C#为课程号，grade为某学号学生学某号课程的考试成绩。今要查询每门课程的平均成绩，且要求查询的结果按平均成绩升序排列，平均成绩相同时，按课程号降序排列，则用SQL查询语言应为 (1) 。 若查询的结果仅限于平均分数超过80分的，则应 (2) 。 |
(1)
A．Select C#，AVG(grad From SCG Group by grade Order by 2，C# Desc
B．Select C#，AVG(grad From SCG Group by C# Order by 2，C# Desc
C．Select C#，AVG(grad From SCG Where C#，AVG Desc Group by grade
D．Select C#，AVG(grad From SCG Group by AVG(grad Order by 2，C# Desc
答案
参考答案：B