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+--Активность пользователей
+
+CREATE MATERIALIZED VIEW user_activity_summary AS
+
+--CTE кол-во курсов на которые записан пользователь
+WITH enrollment_count AS (
+	SELECT 
+		pe.user_id,
+		COUNT(*) AS enrollment_count
+	FROM pet_enrollments pe 
+	GROUP BY pe.user_id
+),
+--CTE просмотренные уникальные уроки пользователем (кол-во)
+viewed_lessons_count AS (
+	SELECT 
+		plv.user_id,
+		DENSE_RANK() OVER(
+			PARTITION BY plv.user_id
+			ORDER BY plv.lesson_id
+		) AS viewed_lessons_count
+	FROM  pet_lesson_views plv 
+),
+
+--CTE дата и время последнего просмотра урока
+last_view AS (
+	SELECT 
+		plv.user_id,
+		LAST_VALUE(plv.viewed_at) OVER (
+			PARTITION BY plv.user_id
+			ORDER BY plv.viewed_at
+			ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING 
+		) AS last_view
+	FROM pet_lesson_views plv
+),
+
+--CTE дата и время первого просмотра урока
+first_view AS (
+	SELECT 
+		plv.user_id,
+		FIRST_VALUE(plv.viewed_at) OVER (
+			PARTITION BY plv.user_id
+			ORDER BY plv.viewed_at 
+		) AS first_view
+	FROM pet_lesson_views plv
+)
+
+SELECT 
+	pu.id AS user_id, 
+	pu.name AS name,
+	ec.enrollment_count AS enrollment_count,
+	MAX(vlc.viewed_lessons_count) AS viewed_lessons_count,
+	last_view,
+	first_view,
+	ROUND(MAX(vlc.viewed_lessons_count * 100.0 / (SELECT COUNT(*) FROM pet_lessons pl)), 2) || '%' AS engagement_rate
+	
+FROM pet_users pu 
+LEFT JOIN enrollment_count ec ON pu.id = ec.user_id
+LEFT JOIN viewed_lessons_count vlc ON pu.id = vlc.user_id 
+LEFT JOIN last_view lv ON pu.id = lv.user_id
+LEFT JOIN first_view fv ON pu.id = fv.user_id
+
+GROUP BY pu.id, ec.enrollment_count, last_view, first_view
+ORDER BY pu.id;