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求选修课程号为 1 或课程号为 2 学生的学号、课程号与成绩,结果按课程号升序、成绩降序排序。
A.
select * from sc where cno ='1' or cno ='2' order by cno asc , grade desc ;
B.
select * from sc where cno ='1 'and cno ='2' order by cno asc , grade desc ;
C.
select * from sc where cno ='1 'or cno ='2' group by cno asc , grade desc ;
D.
select * from sc where cno ='1' or cno ='2' order by cno desc , grade asc ;