sql - 我不知道这个功能有什么问题

Question

嘿...我有这个数据库，我需要创建一个函数来返回通过某个科目的学生的百分比，但我不知道我做错了什么...你能帮帮我吗？？？这是我的图表 这是我的功能...

create function fnPassedStudents(@Semester varchar(7),@CodSubjects varchar(5))
returns @Passed
TABLE (
Semester varchar(7),
Cod_Subjects varchar(5),
Name_Subjects varchar(80),
Nro_Students int,
Nro_Passed float,
Nro_Failed float,
PercentagePassed varchar(4))
as
begin
declare @NroPassed float
select @NroPassed = count(M.Cod_Student)
from Matricula M inner join Subjects A on M.Cod_Subjects = A.Cod_Subjects
Where M.Semester=@Semester and M.Cod_Subjects = @CodSubjects and M.Grade>=10

insert into @Passed 
select M.Semester, A.Cod_Subjects, A.Name_Subjects, COUNT(M.Cod_Student) as Total, 
@NroPassed as Passed, (COUNT(M.Cod_Student) - @NroPassed) as Failed,
((@NroPassed * 100)/(count(M.Cod_Student))) as PercentagePassed
from Matricula M inner join Subjects A on M.Cod_Subjects = A.Cod_Subjects
Group by M.Semester, A.Cod_Subjects, A.Name_Subjects
return  
end
go

我不确定这些信息是否足够...但请耐心等待，我会添加您需要的任何内容...谢谢!!!

Answer 1

create function fnPassedStudents(@Semester varchar(7),@CodSubjects varchar(5))
returns @Passed
TABLE (
Semester varchar(7),
Cod_Subjects varchar(5),
Name_Subjects varchar(80),
Nro_Students int,
Nro_Passed float,
Nro_Failed float,
PercentagePassed varchar(4))
as
begin
insert into @Passed 
select
    M.Semester,
    A.Cod_Subjects,
    A.Name_Subjects,
    count(distinct M.cod_student),
    count(case when M.Grade>=10 then 1 end),
    count(*) - count(case when M.Grade>=10 then 1 end),
    count(case when M.Grade>=10 then 1 end) / count(distinct M.cod_student) * 100
from Matricula M
inner join Subjects A on M.Cod_Subjects = A.Cod_Subjects
Group by M.Semester, A.Cod_Subjects, A.Name_Subjects
return  
end
go

成分

• 案例 http://msdn.microsoft.com/en-us/library/ms181765.aspx
• 不同的 http://msdn.microsoft.com/en-us/library/ms176104.aspx

count(distinct M.cod_student) - 参加一个学期/科目的学生人数case when M.Grade>=10 then 1 end - 通过时生成 1，否则为 null。 NULL 不计算在内count(*) - count(case..) - passed = failed 的补码