fix course_summary and user_activity files

skonev/postgresql/dm_course_summary.sql

@@ -13,25 +13,33 @@ GROUP BY c.id, c.title
 courses_views AS (
     SELECT 
         l.course_id, 
-        COUNT(DISTINCT l.id) AS lessons_count,
         COUNT(lv.id) AS total_views,
         MAX(lv.viewed_at) AS last_viewed_at,
         MIN(lv.viewed_at) AS first_viewed_at
     FROM lessons l
     JOIN lesson_views lv ON l.id = lv.lesson_id 
     GROUP BY l.course_id
+),
+courses_lessons AS (
+	SELECT
+		course_id,
+		COUNT(DISTINCT id) AS lessons_count
+	FROM lessons
+	GROUP BY course_id
 )
+
 SELECT 
 	cu.course_id,
 	cu.course_name,
 	cu.unique_users,
-	cv.lessons_count,
+	cl.lessons_count,
 	cv.total_views,
 	ROUND(cv.total_views::DECIMAL / NULLIF(cu.unique_users, 0), 2) AS avg_views_per_user,
 	cv.first_viewed_at,
 	cv.last_viewed_at
 FROM courses_users cu
 LEFT JOIN courses_views cv USING(course_id)
+LEFT JOIN courses_lessons cl USING(course_id)
 ORDER BY cu.course_id;
 
 COMMIT;