我的存储函数似乎运行不佳，公式是正确的，但它的结果或答案是错误的

Question

---This is my STORED FUNCTION

CREATE FUNCTION calculate_average_grade(student_id INT)
RETURNS DECIMAL(5, 2)
BEGIN
    DECLARE avg_grade DECIMAL(5, 2);

    SELECT AVG((student_midterm_grade + student_final_grade) / 2) INTO avg_grade
    FROM students
    WHERE student_id = student_id;

    RETURN avg_grade;
END //

DELIMITER 

Answer 1

CREATE FUNCTION calculate_average_grade(@student_id INT)
RETURNS DECIMAL(5, 2)
BEGIN
    DECLARE avg_grade DECIMAL(5, 2);

    SELECT (student_midterm_grade + student_final_grade) / 2 INTO avg_grade
    FROM students
    WHERE student_id = @student_id;

    RETURN avg_grade;
END //

DELIMITER 

(student_midterm_grade + Student_final_grade) / 2 这是平均值的公式，因为您通过传递 Student_id 来计算一名学生