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sql 查询最高分、最低分和平均分语句

程序员文章站 2024-04-03 10:39:52
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sql 查询最高分、最低分和平均分语句
//我们要用就以学生成绩为实例吧
/*
结构

学生表
Student(S#,Sname,Sage,Ssex) --S# 学生编号,Sname 学生姓名,Sage 出生年月,Ssex 学生性别
--2.课程表
Course(C#,Cname,T#) --C# --课程编号,Cname 课程名称,T# 教师编号


*/

查询各科成绩最高分、最低分和平均分:以如下形式显示:课程ID,课程name,最高分,最低分,平均分,及格率,中等率,优良率,优秀率
--及格为>=60,中等为:70-80,优良为:80-90,优秀为:>=90
--方法1
select m.C# [课程编号], m.Cname [课程名称],
max(n.score) [最高分],
min(n.score) [最低分],
cast(avg(n.score) as decimal(18,2)) [平均分],
cast((select count(1) from SC where C# = m.C# and score >= 60)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [及格率(%)],
cast((select count(1) from SC where C# = m.C# and score >= 70 and score cast((select count(1) from SC where C# = m.C# and score >= 80 and score cast((select count(1) from SC where C# = m.C# and score >= 90)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [优秀率(%)]
from Course m , SC n
where m.C# = n.C#
group by m.C# , m.Cname
order by m.C#
--方法2
select m.C# [课程编号], m.Cname [课程名称],
(select max(score) from SC where C# = m.C#) [最高分],
(select min(score) from SC where C# = m.C#) [最低分],
(select cast(avg(score) as decimal(18,2)) from SC where C# = m.C#) [平均分],
cast((select count(1) from SC where C# = m.C# and score >= 60)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [及格率(%)],
cast((select count(1) from SC where C# = m.C# and score >= 70 and score cast((select count(1) from SC where C# = m.C# and score >= 80 and score cast((select count(1) from SC where C# = m.C# and score >= 90)*100.0 / (select count(1) from SC where C# = m.C#) as decimal(18,2)) [优秀率(%)]
from Course m
order by m.C#