MySQL查詢返回學分

Question

有三個表的數量（學生，年級，課程）

table1: students 
Name , Id 
Joseph, 1 
David , 2 

table2: grade 
Id(fk of students.id) , Course(fk of course.courseName),Grade 
1 , math101 , A 
1 , math103 , B 
1 , eng201 , A 
2 , eng201 , B 
2 , math103, B 

table3: course 
courseName , credits 
math101 , 3 
math103 , 4 
eng201 , 3 

我想每個名稱與學分總數，他/她賺

QUERY... 
result --> 

ID,NAME,TotalCredit 
1,Joseph,10 
2,David,7 

Answer 1

試試這個：

SELECT s.id, s.name, sum(c.credits) 
    FROM students as s 
LEFT JOIN grade as g on s.id = g.id 
LEFT JOIN course as c on g.course = c.courseName 
GROUP BY s.id, s.name