From c90c7c2b092400f6cb54b6cd1b45593349448694 Mon Sep 17 00:00:00 2001 From: dr0zd Date: Sun, 4 Jan 2026 22:59:36 +0700 Subject: [PATCH 1/6] completed stage 1 creation tables and relations --- mdrozdov/postgresql/create_tables.sql | 70 +++++++++++++++++++ .../postgresql/dm_user_activity_summary.sql | 0 2 files changed, 70 insertions(+) create mode 100644 mdrozdov/postgresql/create_tables.sql create mode 100644 mdrozdov/postgresql/dm_user_activity_summary.sql diff --git a/mdrozdov/postgresql/create_tables.sql b/mdrozdov/postgresql/create_tables.sql new file mode 100644 index 0000000..4b6f588 --- /dev/null +++ b/mdrozdov/postgresql/create_tables.sql @@ -0,0 +1,70 @@ +--drop table is exists users; +create table users( + id int primary key, + name varchar(50) not null, + age int not null, + email varchar(50) not null, + registration_date date not null default current_date +) + +insert into users (id, name, age, email, registration_date) values +(1, 'Alice', 25, 'alice@mail.com', '2023-01-10'), +(2, 'Bob', 30, 'bob@gmail.com', '2023-02-05'), +(3, 'Charlie',22, 'charlie@mail.com', '2023-02-20'), +(4, 'Diana', 28, 'diana@mail.com', '2023-03-01'), +(5, 'Ethan', 35, 'ethan@gmail.com', '2023-03-10') + +create table courses( + id int primary key, + title text not null, + category varchar(30) not null, + created_at date not null default current_date +) + +insert into courses (id, title, category, created_at) values +(1, 'SQL для начинающих', 'data', '2023-01-01'), +(2, 'Python для анализа данных', 'programming', '2023-01-15'), +(3, 'BI с нуля', 'business', '2023-03-01'); + +create table lessons( + id int primary key, + course_id int references courses(id), + title text not null, + duration_min int +) + +insert into lessons (id, course_id, title, duration_min) values +(1, 1, 'SELECT и FROM', 10), +(2, 1, 'JOIN', 15), +(3, 2, 'Pandas', 20), +(4, 3, 'Основы BI', 12), +(5, 3, 'Метрики и дашборды', 18) + +create table enrollments( + id int primary key, + user_id int references users(id), + course_id int references courses(id), + enrolled_at date not null default current_date +) + +insert into enrollments (id, user_id, course_id, enrolled_at) values +(1, 1, 1, '2023-01-15'), +(2, 1, 2, '2023-02-01'), +(3, 2, 1, '2023-01-20'), +(4, 3, 2, '2023-03-05'), +(5, 4, 3, '2023-04-01') + +create table lessons_views( + id int primary key, + user_id int references users(id), + lesson_id int references lessons(id), + viewed_at timestamp not null default now() +) + +insert into lessons_views(id, user_id, lesson_id, viewed_at) values +(1, 1, 1, '2023-01-16 10:00:00'), +(2, 1, 2, '2023-01-16 10:15:00'), +(3, 2, 1, '2023-01-21 09:00:00'), +(4, 3, 3, '2023-03-06 12:00:00'), +(5, 4, 4, '2023-04-02 10:00:00'), +(6, 4, 5, '2023-04-03 10:00:00') \ No newline at end of file diff --git a/mdrozdov/postgresql/dm_user_activity_summary.sql b/mdrozdov/postgresql/dm_user_activity_summary.sql new file mode 100644 index 0000000..e69de29 From 45a59582e03e81cf719d07e89dd766b1c97b412f Mon Sep 17 00:00:00 2001 From: dr0zd Date: Mon, 5 Jan 2026 03:29:12 +0700 Subject: [PATCH 2/6] user_activity_summary materialized view --- .../postgresql/dm_user_activity_summary.sql | 84 +++++++++++++++++++ 1 file changed, 84 insertions(+) diff --git a/mdrozdov/postgresql/dm_user_activity_summary.sql b/mdrozdov/postgresql/dm_user_activity_summary.sql index e69de29..f2539b6 100644 --- a/mdrozdov/postgresql/dm_user_activity_summary.sql +++ b/mdrozdov/postgresql/dm_user_activity_summary.sql @@ -0,0 +1,84 @@ +CREATE MATERIALIZED VIEW dm_user_activity_summary as +with enrollment_counts as( + select user_id, + count(course_id) as enrollment_count + from enrollments e + group by user_id +),views as( + select user_id, + count(distinct lesson_id) as viewed_lessons_count, + min(viewed_at) as first_view, + max(viewed_at) as last_view + from lessons_views + group by user_id +), total_lessons as( + select user_id, + count(*) as total_lessons + from enrollments e + join lessons using(course_id) + group by user_id + order by user_id +), engagment_rate as ( + select tl.user_id, round(v.viewed_lessons_count*100.0/total_lessons, 2) as engagment_rate + from total_lessons tl + join views v using(user_id) +) +select u.id, u.name, enrollment_count, viewed_lessons_count, last_view, first_view, engagment_rate +from users u +join enrollment_counts ec on u.id = ec.user_id +join views v on u.id = v.user_id +join engagment_rate er on u.id = er.user_id +order by u.id +/* +--первая попытка сделать витрину, делал избыточно с проверкой каждого подзапроса, поэтому забыл убрать order by, а также больше практиковался в оконных функциях +CREATE MATERIALIZED VIEW user_activity_summary as +with enrollment_counts as( + select distinct user_id, + count(course_id) over (partition by user_id) as enrollment_count + from enrollments e + order by user_id +), viewed_lessons_count as ( + select + user_id, count(distinct lesson_id) as viewed_lessons_count + from lessons_views lv + group by user_id + order by user_id +), first_views as( + select + user_id, + viewed_at, + row_number() over (partition by user_id order by viewed_at asc) as rnf + from lessons_views +), last_views as( + select + user_id, + viewed_at, + row_number() over (partition by user_id order by viewed_at desc) as rnl + from lessons_views +), result_views as( + select user_id, + fw.viewed_at as first_view, + lw.viewed_at as last_view + from first_views fw + join last_views lw using(user_id) + where rnf = 1 and rnl = 1 +), total_lessons as( + select user_id, + count(*) as total_lessons + from enrollments e + join lessons using(course_id) + group by user_id + order by user_id +), engagment_rate as ( + select tl.user_id, round(vlc.viewed_lessons_count*100.0/total_lessons, 2) as engagment_rate + from total_lessons tl + join viewed_lessons_count vlc using(user_id) +) +select u.id, u.name, enrollment_count, viewed_lessons_count, last_view, first_view, engagment_rate +from users u +join enrollment_counts ec on u.id = ec.user_id +join viewed_lessons_count vlc on u.id = vlc.user_id +join result_views rv on u.id = rv.user_id +join engagment_rate er on u.id = er.user_id +order by u.id +*/ \ No newline at end of file From 23bb973ab04753f7997335c3e856eb1318202fa8 Mon Sep 17 00:00:00 2001 From: dr0zd Date: Mon, 5 Jan 2026 22:56:56 +0700 Subject: [PATCH 3/6] course_summary materialized view --- mdrozdov/postgresql/dm_course_summary.sql | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) create mode 100644 mdrozdov/postgresql/dm_course_summary.sql diff --git a/mdrozdov/postgresql/dm_course_summary.sql b/mdrozdov/postgresql/dm_course_summary.sql new file mode 100644 index 0000000..17a84a4 --- /dev/null +++ b/mdrozdov/postgresql/dm_course_summary.sql @@ -0,0 +1,16 @@ +create materialized view dm_course_summary as +select + e.course_id, + c.title, + count(distinct e.user_id) as unique_users, + count(distinct l.id) as lessons_count, + count(distinct lv.id) as total_views, + count(distinct lv.id)*1.0/count(distinct e.user_id) as avg_views_per_user, + min(lv.viewed_at) as first_viewed_at, + max(lv.viewed_at) as last_viewed_at +from enrollments e +join courses c on e.course_id = c.id +join lessons l on c.id = l.course_id +join lessons_views lv on lv.lesson_id = l.id +group by e.course_id, c.title +order by e.course_id From 1ffc98b49d6be45b179d67de94f30722e577c30d Mon Sep 17 00:00:00 2001 From: dr0zd Date: Mon, 5 Jan 2026 22:59:05 +0700 Subject: [PATCH 4/6] added round in avg_views_per_user --- mdrozdov/postgresql/dm_course_summary.sql | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mdrozdov/postgresql/dm_course_summary.sql b/mdrozdov/postgresql/dm_course_summary.sql index 17a84a4..434ffe3 100644 --- a/mdrozdov/postgresql/dm_course_summary.sql +++ b/mdrozdov/postgresql/dm_course_summary.sql @@ -5,7 +5,7 @@ select count(distinct e.user_id) as unique_users, count(distinct l.id) as lessons_count, count(distinct lv.id) as total_views, - count(distinct lv.id)*1.0/count(distinct e.user_id) as avg_views_per_user, + round(count(distinct lv.id)*1.0/count(distinct e.user_id), 2) as avg_views_per_user, min(lv.viewed_at) as first_viewed_at, max(lv.viewed_at) as last_viewed_at from enrollments e From c1d1796679616a03dc89bc004927b7ea8a30b57d Mon Sep 17 00:00:00 2001 From: dr0zd Date: Tue, 6 Jan 2026 01:41:49 +0700 Subject: [PATCH 5/6] platform_summary materialized view --- mdrozdov/postgresql/dm_platform_summary.sql | 8 ++++++++ 1 file changed, 8 insertions(+) create mode 100644 mdrozdov/postgresql/dm_platform_summary.sql diff --git a/mdrozdov/postgresql/dm_platform_summary.sql b/mdrozdov/postgresql/dm_platform_summary.sql new file mode 100644 index 0000000..7be6f5c --- /dev/null +++ b/mdrozdov/postgresql/dm_platform_summary.sql @@ -0,0 +1,8 @@ +create materialized view dm_platform_summary as +select + (select count(id) from users) as total_users, + (select count(id) from courses) as total_courses, + (select count(id) from lessons) as total_lessons, + (select count(distinct user_id) from lessons_views) as users_with_views, + round((select count(id) from lessons)*1.0/(select count(id) from courses), 2) as avg_lessons_per_course, + (select count(id) from lessons_views)*1.0/(select count(id) from lessons) \ No newline at end of file From 88db25d7d559ffc6b121bcf5782a29429f966226 Mon Sep 17 00:00:00 2001 From: dr0zd Date: Tue, 6 Jan 2026 16:36:58 +0700 Subject: [PATCH 6/6] added safety div with nullif --- mdrozdov/postgresql/dm_course_summary.sql | 2 +- mdrozdov/postgresql/dm_platform_summary.sql | 4 ++-- mdrozdov/postgresql/dm_user_activity_summary.sql | 2 +- 3 files changed, 4 insertions(+), 4 deletions(-) diff --git a/mdrozdov/postgresql/dm_course_summary.sql b/mdrozdov/postgresql/dm_course_summary.sql index 434ffe3..40b4b8d 100644 --- a/mdrozdov/postgresql/dm_course_summary.sql +++ b/mdrozdov/postgresql/dm_course_summary.sql @@ -5,7 +5,7 @@ select count(distinct e.user_id) as unique_users, count(distinct l.id) as lessons_count, count(distinct lv.id) as total_views, - round(count(distinct lv.id)*1.0/count(distinct e.user_id), 2) as avg_views_per_user, + round(count(distinct lv.id)*1.0/nullif(count(distinct e.user_id), 0), 2) as avg_views_per_user, min(lv.viewed_at) as first_viewed_at, max(lv.viewed_at) as last_viewed_at from enrollments e diff --git a/mdrozdov/postgresql/dm_platform_summary.sql b/mdrozdov/postgresql/dm_platform_summary.sql index 7be6f5c..146fde7 100644 --- a/mdrozdov/postgresql/dm_platform_summary.sql +++ b/mdrozdov/postgresql/dm_platform_summary.sql @@ -4,5 +4,5 @@ select (select count(id) from courses) as total_courses, (select count(id) from lessons) as total_lessons, (select count(distinct user_id) from lessons_views) as users_with_views, - round((select count(id) from lessons)*1.0/(select count(id) from courses), 2) as avg_lessons_per_course, - (select count(id) from lessons_views)*1.0/(select count(id) from lessons) \ No newline at end of file + round((select count(id) from lessons)*1.0/nullif((select count(id) from courses), 0), 2) as avg_lessons_per_course, + round((select count(id) from lessons_views)*1.0/nullif((select count(id) from lessons), 0), 2) as avg_views_per_lesson \ No newline at end of file diff --git a/mdrozdov/postgresql/dm_user_activity_summary.sql b/mdrozdov/postgresql/dm_user_activity_summary.sql index f2539b6..413d937 100644 --- a/mdrozdov/postgresql/dm_user_activity_summary.sql +++ b/mdrozdov/postgresql/dm_user_activity_summary.sql @@ -19,7 +19,7 @@ with enrollment_counts as( group by user_id order by user_id ), engagment_rate as ( - select tl.user_id, round(v.viewed_lessons_count*100.0/total_lessons, 2) as engagment_rate + select tl.user_id, round(v.viewed_lessons_count*100.0/nullif(total_lessons), 2) as engagment_rate from total_lessons tl join views v using(user_id) )