Full pet-project

amaksatov/postgresql/OS-330.sql

@@ -14,3 +14,55 @@ LEFT JOIN lesson_views lv ON lv.user_id = e.user_id -- связь lessons с les
 JOIN lessons l ON l.course_id = e.course_id  -- связь уроков с курсами пользователя
 GROUP BY u.id, u.name -- группировка по user_id и name
 ORDER BY user_id; -- сортировка по user_id
+
+
+CREATE MATERIALIZED VIEW course_summary AS
+SELECT
+    c.id AS course_id,
+    c.title AS course_title,
+    COUNT(DISTINCT e.user_id) AS unique_users,
+    COUNT(DISTINCT l.id) AS lessons_count,
+    COUNT(DISTINCT lv.id) AS total_views,
+    ROUND(
+        CASE
+            WHEN COUNT(DISTINCT e.user_id) = 0 THEN NULL
+            ELSE COUNT(DISTINCT lv.id) * 1.0 / COUNT(DISTINCT e.user_id)
+        END, 2) AS avg_views_per_user,
+    MIN(lv.viewed_at) AS first_viewed_at,
+    MAX(lv.viewed_at) AS last_viewed_at
+FROM courses c
+LEFT JOIN enrollments e ON e.course_id = c.id
+LEFT JOIN lessons l ON c.id = l.course_id
+LEFT JOIN lesson_views lv ON lv.lesson_id = l.id
+GROUP BY c.id;
+
+
+
+
+
+CREATE MATERIALIZED VIEW platform_summary AS
+WITH
+user_stats AS (
+    SELECT COUNT(*) AS total_users FROM users
+),
+course_stats AS (
+    SELECT COUNT(*) AS total_courses FROM courses
+),
+lesson_stats AS (
+    SELECT COUNT(*) AS total_lessons FROM lessons
+),
+view_stats AS (
+    SELECT COUNT(*) AS total_views, COUNT(DISTINCT user_id) AS users_with_views
+    FROM lesson_views
+)
+
+SELECT
+    u.total_users,
+    c.total_courses,
+    l.total_lessons,
+    v.users_with_views,
+
+    ROUND(l.total_lessons::decimal / NULLIF(c.total_courses, 0), 2) AS avg_lessons_per_course,
+    ROUND(v.total_views::decimal / NULLIF(l.total_lessons, 0), 2) AS avg_views_per_lesson
+
+FROM user_stats u, course_stats c, lesson_stats l, view_stats v;