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';