计算平均成绩点

Question

这个示例代码她只是计算出表3的平均成绩，而不是真正的GPA：SELECT *    FROM（    选择AVG（g.Grade）作为average_grade，g.SSN    从等级g    g.SSN小组）a    内部联接学生在a.ssn = s.ssn;

找出正确的公式：这是我想出的但是不正确     选择 *    FROM（    SELECT SUM（Grade * CreditHour）/（SUM（CreditHour）as average_grade，g.SSN    从等级g    g.SSN小组）a    内部联接学生在a.ssn = s.ssn;

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Answer 1

在我看来，好像你只是忘了加入课程表的成绩表。或者我错过了什么？

SELECT * 
FROM 
( 
  SELECT 
    SUM(g.Grade*c.CreditHour) / SUM(c.CreditHour) as average_grade, 
    g.SSN 
  FROM Grade g
  INNER JOIN Course c ON c.cno = g.cno                         
  GROUP BY g.SSN
) a 
INNER JOIN Student s ON a.ssn = s.ssn;