查詢各科成績最高分、最低分和平均分(case when then else end)
阿新 • • 發佈:2021-01-15
技術標籤:SQL server 筆記sqlmysqlsqlserver
資料,建立表,檢視資料表(程式碼)~
1、查詢各科成績最高分、最低分和平均分:
要求:
– 以如下形式顯示:課程 ID,課程 name,最高分,最低分,平均分,及格率,中等率,優良率,優秀率
– 及格為>=60,中等為:70-80,優良為:80-90,優秀為:>=90
– 要求輸出課程號和選修人數,查詢結果按人數降序排列,若人數相同,按課程號升序排列
select Course.C#,Course.Cname,A.最高分,A.最低分,A.平均分,B.及格率,C.中等率,D.優良率,E.優秀率,F.選修人數
from Course
left join (select C#, max(score) 最高分,min(score) 最低分,AVG(score) 平均分 from SC group by C#
)A on Course.C# = A.C#
left join (select C#,
(convert( decimal(5,2),( sum (case when score >= 60 then 1 else 0 end)*1.00 /count(*) ) )*100) 及格率
from SC group by C#)B on Course.C# = B.C#
left join (select C#,
(convert( decimal(5,2),( sum (case when score >=70 and score<80 then 1 else 0 end)*1.00 /count(*) ) )*100) 中等率
from SC group by C#)C on Course.C# = C.C#
left join (select C#,
(convert( decimal(5,2),( sum (case when score >=80 and score<90 then 1 else 0 end)*1.00 /count(*) ) )*100) 優良率
from SC group by C#)D on Course.C# = D.C#
left join (select C#,
(convert( decimal(5,2),( sum (case when score >=90 then 1 else 0 end)*1.00 /count(*) ) )*100) 優秀率
from SC group by C#)E on Course.C# = E.C#
left join (select C#,count(S#) 選修人數
from SC group by C#)F on Course.C# = F.C# order by F.選修人數 desc,Course.C# asc
2、統計各科成績各分數段人數:課程編號,課程名稱,[100-85],[85-70],[70-60],[60-0] 及所佔百分比
select Course.C#,Course.Cname,A.[100-85],A.所佔百分比 ,
B.[85-70],B.所佔百分比 , C.[70-60],C.所佔百分比 , D.[60-0],D.所佔百分比 from Course
left join (select C#,sum (case when score >85 then 1 else 0 end) [100-85],
(convert( decimal(5,2),( sum (case when score >85 then 1 else 0 end)*1.00 /count(*) ) )*100) 所佔百分比
from SC group by C#)A on Course.C# = A.C#
left join (select C#,sum (case when score >70 and score<=85 then 1 else 0 end) [85-70],
(convert( decimal(5,2),( sum (case when score >70 and score<=85 then 1 else 0 end)*1.00 /count(*) ) )*100) 所佔百分比
from SC group by C#)B on Course.C# = B.C#
left join (select C#,sum (case when score >60 and score<=70 then 1 else 0 end) [70-60],
(convert( decimal(5,2),( sum (case when score >60 and score<=70 then 1 else 0 end)*1.00 /count(*) ) )*100) 所佔百分比
from SC group by C#)C on Course.C# = C.C#
left join (select C#,sum (case when score <= 60 then 1 else 0 end) [60-0],
(convert( decimal(5,2),( sum (case when score <= 60 then 1 else 0 end)*1.00 /count(*) ) )*100) 所佔百分比
from SC group by C#)D on Course.C# = D.C#