--lesson_popularity_summary data mart
	create materialized view dm.lesson_popularity_summary as
	select 
		dl.lesson_id,
		dl.title as lesson_title,
		dl.course_id,
		dc.title as course_title,
		count(flv.lesson_id) as total_views,
		count(distinct flv.user_id) as unique_users,
		min(flv.viewed_at) as first_view,
		max(flv.viewed_at) as last_view
	from core.dim_lesson dl
	left join core.dim_course dc 
	    on dl.course_id = dc.course_id
	left join core.fact_lesson_views flv 
	    on dl.lesson_id = flv.lesson_id
	group by dl.lesson_id, dl.title, dl.course_id, dc.title
	
	-- inactive_users_summary data mart
	create materialized view dm.inactive_users_summary as
	select
		du.user_id,
		du.name as user_name,
		du.email,
		du.age,
		count(e.course_id) as enrollments_count,
		du.registration_date
	from core.dim_user du
	left join core.enrollments e 
		on du.user_id = e.user_id
	left join core.fact_lesson_views flv 
		on du.user_id = flv.user_id
	where flv.user_id is null
	group by du.user_id, du.name, du.email, du.age, du.registration_date
	
	-- course_completion_rate data mart
	create materialized view dm.course_completion_rate as
	with total_lessons_per_course as(
		select
			course_id,
			count(*) as lessons_in_course
		from core.dim_lesson
		group by course_id
	), lessons_viewed as (
		select 
			user_id,
			course_id,
			count(*) as lessons_viewed
		from fact_lesson_views flv
		group by user_id, course_id
	)
	select 
		du.user_id as user_id,
		du.name as user_name,
		dc.course_id as course_id,
		dc.title as course_title,
		tlpc.lessons_in_course,
		coalesce(lv.lessons_viewed, 0) as lessons_viewed,
		round(
			coalesce(
				coalesce(lv.lessons_viewed, 0)*1.0/nullif(tlpc.lessons_in_course, 0), 0
				), 2) as completion_rate
	from core.enrollments e
	join core.dim_user du 
		on e.user_id = du.user_id
	join total_lessons_per_course tlpc
		on tlpc.course_id = e.course_id
	join core.dim_course dc
		on e.course_id = dc.course_id
	left join lessons_viewed lv
		on du.user_id = lv.user_id and dc.course_id = lv.course_id