CREATE OR REPLACE FUNCTION compare_lessons(d_week DATE, teacher VARCHAR)
returns VARCHAR AS $$
DECLARE
    lesson1 VARCHAR(100);
    lesson2 VARCHAR(100);
    lesson3 VARCHAR(100);
    lesson4 VARCHAR(100);
    lesson5 VARCHAR(100);
    lesson6 VARCHAR(100);
BEGIN
    SELECT c.name INTO lesson1 FROM coprs c, audiences a, sheldule h, teachers t
    WHERE c.id = a.corp_id
        AND a.id = h.audience_id
        AND t.id = h.teacher_id
        AND t.name = teacher
        AND h.day_week = d_week
        AND h.lesson_id = '1';

    SELECT c.name INTO lesson2 FROM coprs c, audiences a, sheldule h, teachers t
    WHERE c.id = a.corp_id
        AND a.id = h.audience_id
        AND t.id = h.teacher_id
        AND t.name = teacher
        AND h.day_week = d_week
        AND h.lesson_id = '2';

    SELECT c.name INTO lesson3 FROM coprs c, audiences a, sheldule h, teachers t
    WHERE c.id = a.corp_id
        AND a.id = h.audience_id
        AND t.id = h.teacher_id
        AND t.name = teacher
        AND h.day_week = d_week
        AND h.lesson_id = '3';

    SELECT c.name INTO lesson1 FROM coprs c, audiences a, sheldule h, teachers t
    WHERE c.id = a.corp_id
        AND a.id = h.audience_id
        AND t.id = h.teacher_id
        AND t.name = teacher
        AND h.day_week = d_week
        AND h.lesson_id = '4';

    SELECT c.name INTO lesson5 FROM coprs c, audiences a, sheldule h, teachers t
    WHERE c.id = a.corp_id
        AND a.id = h.audience_id
        AND t.id = h.teacher_id
        AND t.name = teacher
        AND h.day_week = d_week
        AND h.lesson_id = '5';

    SELECT c.name INTO lesson1 FROM coprs c, audiences a, sheldule h, teachers t
    WHERE c.id = a.corp_id
        AND a.id = h.audience_id
        AND t.id = h.teacher_id
        AND t.name = teacher
        AND h.day_week = d_week
        AND h.lesson_id = '6';

    IF(lesson1 != lesson2)OR(lesson2 != lesson3)OR(lesson3 != lesson4)OR(lesson4 != lesson5)OR(lesson5 != lesson6)
    THEN
        RETURN teacher;
    ELSE
        RETURN 'none';
    END IF;
END;
$$  LANGUAGE plpgsql;

SELECT DISTINCT compare_lessons(h.day_date, t.name) FROM sheldule h, teachers t, audiences a, corps c
WHERE t.id = h.teacher_id
    AND c.id = a.corp_id
    AND a.id = h.audience_id
    AND h.day_date BETWEEN TO_DATE('2022-01-07','YYYY-MM-DD') AND TO_DATE('2022-07-01','YYYY-MM-DD')
    AND compare_lessons(h.day_date, t.name) != 'none';