我必须创建一个具有计数,总和但值不佳的报告(红色)
SQL FIDDLE:http://sqlfiddle.com/#!9 / 9aba2d / 2/0
这是我的查询:
select
courses.id_courses,
courses.name_courses,
count(DISTINCT list_courses_prof.id_courses_prof) AS nbProfessors,
count(DISTINCT list_courses_stud.id_courses_stud) AS nbStudents,
sum(if(list_courses_stud.present_stud > 0,1,0)) AS nbPresents,
concat(round(sum(if(list_courses_stud.present_stud > 0,1,0)) / count(list_courses_stud.id_courses_stud) * 100,0),'%') AS pctPresent,
sum(if(list_gender.name_gender = 'Man',1,0)) AS NbMan,
concat(round(sum(if(list_gender.name_gender = 'Man',1,0)) / count(list_courses_stud.id_courses_stud) * 100,0),'%') AS pctMan,
sum(if(list_gender.name_gender = 'Woman',1,0)) AS NbWoman,
concat(round(sum(if(list_gender.name_gender = 'Woman',1,0)) / count(list_courses_stud.id_courses_stud) * 100,0),'%') AS pctWoman
from courses
left join list_courses_stud on courses.id_courses = list_courses_stud.id_courses_join
left join list_courses_prof on courses.id_courses = list_courses_prof.id_courses_join
left join students on list_courses_stud.id_student_join = students.id_student
left join list_gender on students.id_gender_join = list_gender.id_gender
group by courses.id_courses
order by courses.id_courses desc;
代码的问题在于,您没有为每种情况都计算出不同的学生。
尝试这个:
select c.id_courses, c.name_courses,
count(DISTINCT cp.id_courses_prof) AS nbProfessors,
count(DISTINCT s.id_student) AS nbStudents,
count(DISTINCT CASE WHEN cs.present_stud > 0 THEN s.id_student END) AS nbPresents,
concat(round(sum(cs.present_stud > 0) / count(cs.id_courses_stud) * 100, 0), '%') AS pctPresent,
count(DISTINCT CASE WHEN g.name_gender = 'Man' THEN s.id_student END) AS NbMan,
concat(round(count(DISTINCT CASE WHEN g.name_gender = 'Man' THEN s.id_student END) / count(DISTINCT s.id_student) * 100, 0), '%') AS pctMan,
count(DISTINCT CASE WHEN g.name_gender = 'Woman' THEN s.id_student END) AS NbWoman,
concat(round(count(DISTINCT CASE WHEN g.name_gender = 'Woman' THEN s.id_student END) / count(DISTINCT s.id_student) * 100, 0), '%') AS pctWoman
from courses c
left join list_courses_stud cs on c.id_courses = cs.id_courses_join
left join list_courses_prof cp on c.id_courses = cp.id_courses_join
left join students s on cs.id_student_join = s.id_student
left join list_gender g on s.id_gender_join = g.id_gender
group by c.id_courses, c.name_courses
order by c.id_courses desc;
参见演示。
结果:
| id_courses | name_courses | nbProfessors | nbStudents | nbPresents | pctPresent | NbMan | pctMan | NbWoman | pctWoman |
| ---------- | ------------ | ------------ | ---------- | ---------- | ---------- | ----- | ------ | ------- | -------- |
| 3 | Technnology | 3 | 3 | 2 | 67% | 2 | 67% | 1 | 33% |
| 2 | Music | 2 | 2 | 2 | 100% | 2 | 100% | 0 | 0% |
| 1 | Paint | 1 | 5 | 4 | 80% | 3 | 60% | 2 | 40% |
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