---

UPDATE Grades
SET grade = 4
WHERE student_id = 4 AND subject_id = 3;

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SELECT
    Students.student_id,
    Students.last_name,
    Students.first_name,
    MIN(Grades.grade) AS min_grade,
    MAX(Grades.grade) AS max_grade,
    ROUND(AVG(Grades.grade), 2) AS avg_grade
FROM Students
JOIN Grades ON Students.student_id = Grades.student_id
GROUP BY Students.student_id, Students.last_name, Students.first_name;

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SELECT
    Students.student_id,
    Students.last_name,
    Students.first_name,
    SUM(Grades.grade) AS total_sum
FROM Students
JOIN Grades ON Students.student_id = Grades.student_id
GROUP BY Students.student_id, Students.last_name, Students.first_name
ORDER BY total_sum DESC;

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SELECT
    Students.student_id,
    Students.last_name,
    Students.first_name,
    SUM(Grades.grade) AS total_sum
FROM Students
JOIN Grades ON Students.student_id = Grades.student_id
GROUP BY Students.student_id, Students.last_name, Students.first_name
HAVING SUM(Grades.grade) > 4;

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BEGIN TRANSACTION;

CREATE TABLE Groups (
    group_name VARCHAR(20) PRIMARY_KEY,
    headman_id INT REFERENCES Students(student_id)
);

INSERT INTO Groups (group_name, headman_id);
VALUES ('ПОИМ-25', 1);
COMMIT;