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[email protected] 9.检索XK数据库的COURSE表的课程信息,要求显示报名人数与限选人数之比.
select *,WillNum/LimitNum as rate from Course
10. 检索课程表中最小的报名人数、最大的报名人数以及平均报名人数.
select min(WillNum) as a,max(WillNum) as b,avg(WillNum) as c from Course
11.检索课程信息(包括报名人数与限选人数之比),要求检索结果按照报名人数升序排序.
select *,WillNum/LimitNum as rate from Course
order by WillNum
26.按课程分类统计平均报名人数.
select kind,avg(WillNum) as '平均数' from Course
group by Kind
27.检索”信息技术”类课程的平均报名人数.
select avg(WillNum) as '平均数' from Course
where Kind='信息技术'
28.检索平均报名人数大于25人的课程分类和类平均报名人数.
select Kind,avg(WillNum) from Course
group by Kind
having avg(WillNum)