Добавил проверку на null в две датамарта

gmokrousov/postgresql/DM_platform_summary.sql

@@ -3,7 +3,7 @@ create materialized view platform_summary as
         lv_stats as (
             select 
                 count(distinct user_id) as users_with_views,
-                count(*)::decimal / count(distinct lesson_id) as avg_views_per_lesson
+                count(*)::decimal / nullif(count(distinct lesson_id), as avg_views_per_lesson
             from lesson_views
     	)
 	select 
@@ -11,7 +11,7 @@ create materialized view platform_summary as
 		total_courses,
 		total_lessons,
 		users_with_views,
-		round((total_lessons::decimal / total_courses), 2) AS avg_lessons_per_course,
+		round((total_lessons::decimal / nullif(total_courses, 2)), 2) AS avg_lessons_per_course,
 		round(avg_views_per_lesson, 2) as avg_views_per_lesson
 	from 
 		(

gmokrousov/postgresql/DM_user_activity_summary.sql

@@ -28,7 +28,7 @@ CREATE MATERIALIZED VIEW user_activity_summary as
         l.viewed_lessons_count,
         l.last_view,
         l.first_view,
-        round(l.viewed_lessons_count::decimal * 100 / en.possible_lessons, 2) as engagement_rate
+        round(l.viewed_lessons_count::decimal * 100 / nullif(en.possible_lessons, 0), 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