Merge pull request 'OS-158' (#23) from OS-158 into main

Reviewed-on: https://gitea.de-infra.servehttp.com/de-infrastructure/DWH/pulls/23
Reviewed-by: aleksey bogatyrev <abogatyrev@example.com>

gmokrousov/postgresql/DM_course_summary.sql

@@ -0,0 +1,24 @@
+CREATE MATERIALIZED VIEW course_summary as 
+    with 
+        lw as (
+            select 
+                user_id,
+                lesson_id,
+                viewed_at 
+            from lesson_views
+        )
+    select
+        id as course_id,
+        title as course_title,
+        count(distinct e.user_id) as unique_users,
+        count(distinct l.lesson_id) as lessons_count,
+        count(distinct lw.viewed_at) as total_views,
+        round(count(distinct lw.viewed_at)::decimal / count(distinct e.user_id), 2) as avg_views_per_user,
+        min(lw.viewed_at) as first_viewed_at,
+        max(lw.viewed_at) as last_viewed_at 
+    from
+        courses as c 
+        join (select course_id, user_id from enrollments) as e on c.id = e.course_id 
+        join (select id as lesson_id, course_id from lessons) as l on c.id = l.course_id 
+        join lw on l.lesson_id = lw.lesson_id 
+    group by id;

gmokrousov/postgresql/DM_platform_summary.sql

@@ -0,0 +1,24 @@
+create materialized view platform_summary as 
+	with 
+        lv_stats as (
+            select 
+                count(distinct user_id) as users_with_views,
+                count(*)::decimal / nullif(count(distinct lesson_id), as avg_views_per_lesson
+            from lesson_views
+    	)
+	select 
+		total_users,
+		total_courses,
+		total_lessons,
+		users_with_views,
+		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 
+		(
+		select 
+			(select count(*) from users) as total_users,
+			(select count(*) from courses) as total_courses,
+			count(*) as total_lessons
+		from lessons
+	) as s
+	cross join lv_stats as lv;

gmokrousov/postgresql/DM_user_activity_summary.sql

@@ -0,0 +1,35 @@
+-- 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 / 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
+    join enrollments_cte as e on u.id = e.user_id;

gmokrousov/postgresql/creating_tables.sql

@@ -0,0 +1,69 @@
+create table users (
+    id serial primary key,
+    name varchar(50) not null,
+    age int not null,
+    email varchar(100) not null,
+    registration_date date not null
+);
+
+insert into users (name, age, email, registration_date) values
+    ('Alice', 25, 'alice@mail.com', ; '2023-01-10'),
+    ('Bob', 30, 'bob@gmail.com', '2023-02-05'),
+    ('Charlie', 22, 'Charlie@mail.com', '2023-02-20'),
+    ('Diana', 28, 'diana@mail.com', '2023-03-01'),
+    ('Ethan', 35, 'ethan@gmail.com', '2023-03-10');
+
+create table courses (
+    id serial primary key,
+    title varchar(100) not null,
+    category varchar(30) not null,
+    created_at date not_null
+);
+
+insert into courses (title, category, created_at) values
+    ('SQL для начинающих', 'data', '2023-01-01'),
+    ('Python для анализа данных', 'programming', '2023-01-15'),
+    ('BI с нуля', 'business', '2023-03-01');
+
+create table lessons (
+    id serial primary key,
+    course_id int references courses(id),
+    title varchar(100) not null,
+    duration_min int not null
+);
+
+insert into lessons (course_id, title, duration_min) values
+    (1, 'SELECT и FROM', 10),
+    (1, 'JOIN', 15),
+    (2, 'Pandas', 20),
+    (3, 'Основы BI', 12),
+    (3, 'Метрики и дашборды', 18);
+
+create table enrollments (
+    id serial primary key,
+    user_id int references users(id),
+    course_id int references courses(id),
+    enrolled_at date not null
+);
+
+insert into enrollments (user_id, course_id, enrolled_at) values
+    (1, 1, '2023-01-15'),
+    (1, 2, '2023-02-01'),
+    (2, 1, '2023-01-20'),
+    (3, 2, '2023-03-05'),
+    (4, 3, '2023-04-01');
+
+create table lesson_views (
+    id serial primary key,
+    user_id int references users(id),
+    lesson_id int references lessons(id),
+    viewed_at timestamp(0) not null
+);
+
+insert into lesson_views (user_id, lesson_id, viewed_at) values
+    (1, 1, '2023-01-16 10:00:00'),
+    (1, 2, '2023-01-16 10:15:00'),
+    (2, 1, '2023-01-21 09:00:00'),
+    (3, 3, '2023-03-06 12:00:00'),
+    (4, 4, '2023-04-02 10:00:00'),
+    (4, 5, '2023-04-03 10:00:00');