Создал витрину активности юзеров

gmokrousov/postgresql/DM_user_activity_summary.sql

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+-- Витрина активности пользователей
+CREATE MATERIALIZED VIEW user_activity_summary as
+ with 
+    lessons_cte as (
+        select 
+            user_id,
+            count (*) as viewed_lessons_count,
+            max(viewed_at) as last_view,
+            min(viewed_at) as first_view
+        from lesson_views
+        group by user_id
+    ),
+    enrollments_cte as (
+        select user_id, count(*) as enrollment_count
+        from enrollments as e 
+        group by user_id
+    ),
+    engagement_cte as (
+        select user_id, count(*) as possible_lessons
+        from lessons as l
+        join enrollments as en on l.course_id = en.course_id
+        group by user_id
+    )   
+    select 
+        id as user_id, 
+        name, 
+        e.enrollment_count,
+        l.viewed_lessons_count,
+        l.last_view,
+        l.first_view,
+        round(l.viewed_lessons_count::decimal * 100 / en.possible_lessons, 2) as engagement_rate
+    from users as u
+    join lessons_cte as l on u.id = l.user_id
+    join engagement_cte as en on u.id = en.user_id
+    join enrollments_cte as e on u.id = e.user_id;