use Xk
go
--拓展小练习：查询课程信息，报名人数占限选人数之比。要求查询结果按报名人数降序排序，（且只显示结果的前10行）
select top 10 percent *,‘报名人数占限选人数之比‘=WillNum/LimitNum from Course order by WillNum desc 
go
--13、查询课程表的教师名，课程号，课程名，要求查询结果按教师名降序排列，教师名相同时，按课程号升序排列。
select Teacher,CouNo,CouName from Course order by Teacher desc, CouNo
go
--14、在课程表中查询周二开设的选修课，要求按上课时间排序查询结果
select * from Course where SchoolTime like ‘周二%‘ order by SchoolTime
go
--拓展小练习：查询非周二开设的选修课
select * from Course where SchoolTime  like ‘周[^二]%‘ order by SchoolTime
go
select * from Course where SchoolTime not like ‘周二%‘ order by SchoolTime
go
--15、查询选课表中随机数无值得数据行（使用is null）
select * from StuCou where RandomNum=‘‘
go
--16、统计Course表中提供了多少门选修课
select COUNT(*) as ‘提供多少门选修课‘ from Course
go
--17、查询课程表中能提供选修课程的总人数。
select SUM(LimitNum) as ‘能提供课程的总人数‘ from Course
go
--18、查看课程表中最少报名人数、最多报名人数和平均报名人数
select MIN(WillNum) as ‘最少报名人数‘, MAX(WillNum) as ‘最多报名人数‘, CONVERT(DECIMAL(5,2),AVG(WillNum)) as ‘平均报名人数‘ from Course
go
--19、按课程类别分组统计各类课程的门数
select Kind as ‘课程类别‘, COUNT(kind) as ‘各类课程的门数‘ from Course group by Kind
go
--20、按课程类别分组统计各类课程的门数，并给出课程的总门数。
select Kind as ‘课程类别‘, COUNT(kind) as ‘各类课程的门数‘ from Course group by Kind with CUBE
go
--21、查看报名人数大于15的各类课程的最少报名人数和最多报名人数
select Kind as ‘课程类别‘, MIN(WillNum) as ‘最少报名人数‘, MAX(WillNum) as ‘最多报名人数‘ from Course where WillNum>15 group by Kind
go
--22、查看报名人数大于15并且每组平均报名人数大于30的课程类别和各组的平均报名人数
select ‘课程类别‘=Kind,‘平均报名人数‘=AVG(WillNum)
from Course
where WillNum>15
group by Kind
having AVG(WillNum)>30
go