PET-project 1st task completed

aharlamcev/postgresql/Pet-projectsql.sql

@@ -200,3 +200,38 @@ VALUES
 (56, 14, 7, '2023-01-11 10:00:00'),
 (57, 14, 8, '2023-01-12 11:00:00'),
 (58, 14, 9, '2023-01-10 08:00:00');
+
+
+---------------------------------------------------------
+-- 1 задание Активные пользователи
+
+create materialized view user_activity_summary AS
+with enroll_count as (
+					select u.id as user_id, u.name as user_name, 
+					COUNT(e.course_id) as enrollment_count
+					from users u
+					join enrollments e on u.id = e.user_id
+					group by u.id, u.name
+					),
+viewed_count as (
+				select ec.user_id, ec.user_name, enrollment_count,
+				COUNT(distinct lv.lesson_id) as viewed_lessons_count,
+				MIN(lv.viewed_at) as first_view,
+				MAX(lv.viewed_at) as last_view
+				from enroll_count ec
+				left join lesson_views lv on ec.user_id = lv.user_id
+				group by ec.user_id, ec.user_name, enrollment_count
+				),
+possible_lessons as (		
+					select u.id as user_id, COUNT(l.id) as poss_lessons 
+					from users u
+					left join enrollments e on u.id = e.user_id
+					left join lessons l on e.course_id = l.course_id 
+					group by u.id
+					)
+select vc.user_id, user_name, enrollment_count, viewed_lessons_count, first_view, last_view, 
+ROUND(100.0 * viewed_lessons_count / pl.poss_lessons, 2) as engagement_rate
+from viewed_count vc
+left join possible_lessons pl on vc.user_id = pl.user_id
+;
+