具有内部联接的sql计数

我有一张缺席者的桌子，那张桌子存放着缺席者的学生

从这个表中，我必须找到总的出席者和总缺席者，为此，我加入了Sections表，该表包含特定部分的最大容量

对此，我的疑问是

select COUNT(Attendance.studentid) as Absentees
        ,Sections.Max-count(studentid) as Presentees
from Attendance
inner join Students
on students.StudentId=Attendance.StudentId
inner join Sections
on Sections.CourseId=students.CourseId
group by Sections.Max

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它的工作很好，同样的方式我如何才能找到性别方面的演示者/缺席者……性别栏在学生表中，有人能告诉我一些想法吗，提前谢谢

只需将性别栏添加到您的

选择…

栏和

分组依据

，您将得到每个性别的一行：

select COUNT(Attendance.studentid) as Absentees,
       Sections.Max-count(studentid) as Presentees,
       Students.Gender as Gender
from Attendance
inner join Students
on Students.StudentId=Attendance.StudentId
inner join Sections
on Sections.CourseId=Students.CourseId
group by Sections.Max, Students.Gender

---

只需将性别列添加到您的

选择…

列和

分组依据

，您将得到每个性别的一行：

select COUNT(Attendance.studentid) as Absentees,
       Sections.Max-count(studentid) as Presentees,
       Students.Gender as Gender
from Attendance
inner join Students
on Students.StudentId=Attendance.StudentId
inner join Sections
on Sections.CourseId=Students.CourseId
group by Sections.Max, Students.Gender