SQL内部连接加总和

Question

有没有一种方法可以显示如下所示的输出以及每人的总金额分配。 在这种情况下，鲍勃·怀特（Bob White）总共有2个作业，其余1个。

我尝试通过assignments.codeassignment进行分组，但是没有用。

SELECT students.namestudent, assignments.homework, 
assignments.codeassignment, courses.codecourse, courses.namecourse
FROM students
INNER JOIN assignments
ON students.idstudent = assignments.idstudent
INNER JOIN courses
on assignments.codecourse = courses.codecourse;

output:
'Jack Brown', 'finnish assignment a', 1111, 123, 'math'
'Alice Black', 'finnish assignment b', 4444, 256, 'algebra'
'Bob White', 'finnish assignment c', 2222, 555, 'game project'
'Dan Purple', 'finnish assignment d', 3333,548, 'analysis'
'Bob White', 'finnish assignment c', 4444, 256, 'algebra'

Answer 1

您可以使用窗口功能：

SELECT s.namestudent, a.homework, a.codeassignment, c.codecourse, c.namecourse,
       COUNT(*) OVER (PARTITION BY s.namestudent)
FROM students s INNER JOIN
     assignments a
     ON s.idstudent = a.idstudent INNER JOIN
     courses c
     ONn a.codecourse = c.codecourse;

COUNT(*) OVER (. . .)是大多数数据库中可用的ANSI标准功能。