Answer #7

DROP TABLE IF EXISTS teachers, сontests, participants;

CREATE TABLE teachers (
    teacher_id serial PRIMARY KEY,
    fio text
);

CREATE TABLE сontests (
    сontest_id serial PRIMARY KEY,
    start_date DATE,
    name text
);

CREATE TABLE participants (
    participant_id serial,
    fio text,
    contest_id INTEGER REFERENCES сontests(сontest_id),
    teacher_id INTEGER REFERENCES teachers(teacher_id),
    RESULT INTEGER
);

INSERT INTO teachers(fio) VALUES
('Иванова И.'),
('Петорва П.'),
('Сидорова С.');

INSERT INTO сontests(start_date, name) VALUES
(to_date('2020', 'YYYY'), 'New Vasuki conference'),
(to_date('2021', 'YYYY'), 'New Vasuki online-conference');

INSERT INTO participants(fio, contest_id, teacher_id, RESULT) VALUES
('Карцев', 2, 1, 1),
('Бендер', 1, 1, 1),
('Угольников', 2 , 2, 8),
('Хазанов', 2, 2, 4),
('Арлазоров', 1, 3, 4),
('Задорнов', 1, 3, 5);

SELECT teachers.teacher_id FROM teachers
JOIN participants USING(teacher_id)
WHERE participants.RESULT NOT BETWEEN 1 AND 3
GROUP BY teachers.teacher_id
HAVING COUNT(participants.teacher_id) = ALL(SELECT COUNT(*) FROM participants GROUP BY participants.teacher_id);

SELECT teachers.teacher_id FROM teachers JOIN
participants USING(teacher_id) JOIN (
  SELECT teacher_id, COUNT(*) AS bad_count FROM participants
  WHERE RESULT NOT BETWEEN 1 AND 3
  GROUP BY teacher_id
) AS tt USING(teacher_id)
GROUP BY teachers.teacher_id, bad_count
HAVING COUNT(participants.teacher_id) = bad_count;