回答：向sc 表中插入一些记录，这些记录要求符合以下条件：没有上过编号“c003”课程的同学学号、“c003”号课的平均成绩；

insert into sc 

select sid,'03',score from

(select '03',avg(score)  score from sc s1 where cid='03')s2

cross join (select distinct sid from sc s3

                where not exists (select 1 from sc s4 where s4.cid='03' and s3.sid=s4.sid))s5

                 on 1=1