From 781cb67a2cf0064596aa330b23489da5d606d418 Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Thu, 8 Jan 2026 19:43:07 +0600
Subject: [PATCH 1/9] add postgresql script.sql

---
 amaksatov/postgresql/script.sql | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 amaksatov/postgresql/script.sql

diff --git a/amaksatov/postgresql/script.sql b/amaksatov/postgresql/script.sql
new file mode 100644
index 0000000..a2b9b92
--- /dev/null
+++ b/amaksatov/postgresql/script.sql
@@ -0,0 +1 @@
+SELECT * FROM table1;
\ No newline at end of file

From 717ba15e01db914b5dbf363ede0082c3df2db66b Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Thu, 8 Jan 2026 19:45:59 +0600
Subject: [PATCH 2/9] test changes

---
 amaksatov/postgresql/script.sql | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/amaksatov/postgresql/script.sql b/amaksatov/postgresql/script.sql
index a2b9b92..e5fbf49 100644
--- a/amaksatov/postgresql/script.sql
+++ b/amaksatov/postgresql/script.sql
@@ -1 +1 @@
-SELECT * FROM table1;
\ No newline at end of file
+SELECT * FROM table3;
\ No newline at end of file

From 47732aa19a9f882e47d0abd954ae4c7465f0e4c0 Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sat, 10 Jan 2026 20:11:38 +0600
Subject: [PATCH 3/9] Done

---
 amaksatov/postgresql/OS-329.sql | 217 ++++++++++++++++++++++++++++++++
 amaksatov/postgresql/script.sql |   1 -
 2 files changed, 217 insertions(+), 1 deletion(-)
 create mode 100644 amaksatov/postgresql/OS-329.sql

diff --git a/amaksatov/postgresql/OS-329.sql b/amaksatov/postgresql/OS-329.sql
new file mode 100644
index 0000000..a3d3ea3
--- /dev/null
+++ b/amaksatov/postgresql/OS-329.sql
@@ -0,0 +1,217 @@
+CREATE TABLE IF NOT EXISTS amaksatov.users (
+    id SERIAL PRIMARY KEY,
+    name VARCHAR(100),
+    age INT,
+    email VARCHAR(255),
+    registration_date DATE
+);
+
+CREATE TABLE IF NOT EXISTS amaksatov.courses (
+    id SERIAL PRIMARY KEY,
+    title VARCHAR(255),
+    category VARCHAR(100),
+    created_at DATE
+);
+
+CREATE TABLE IF NOT EXISTS amaksatov.lessons (
+    id SERIAL PRIMARY KEY,
+    course_id INT,
+    title VARCHAR(255),
+    duration_min INT,
+    FOREIGN KEY (course_id) REFERENCES amaksatov.courses(id)
+);
+
+CREATE TABLE IF NOT EXISTS amaksatov.enrollments (
+    id SERIAL PRIMARY KEY,
+    user_id INT,
+    course_id INT,
+    enrolled_at date,
+    FOREIGN KEY (user_id) REFERENCES amaksatov.users(id),
+    FOREIGN KEY (course_id) REFERENCES amaksatov.courses(id)
+);
+
+CREATE TABLE IF NOT EXISTS amaksatov.lesson_views (
+    id SERIAL PRIMARY KEY,
+    user_id INT,
+    lesson_id INT,
+    viewed_at TIMESTAMP,
+    FOREIGN KEY (user_id) REFERENCES amaksatov.users(id),
+    FOREIGN KEY (lesson_id) REFERENCES amaksatov.lessons(id)
+);
+
+
+INSERT
+    INTO
+    amaksatov.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'
+);
+
+SELECT * FROM amaksatov.users;
+
+
+INSERT
+    INTO
+    amaksatov.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'
+);
+
+INSERT
+    INTO
+    amaksatov.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
+);
+
+INSERT
+    INTO
+    amaksatov.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'
+);
+
+INSERT
+    INTO
+    amaksatov.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'
+);
+
+
+SELECT * FROM amaksatov.lessons
\ No newline at end of file
diff --git a/amaksatov/postgresql/script.sql b/amaksatov/postgresql/script.sql
index e5fbf49..e69de29 100644
--- a/amaksatov/postgresql/script.sql
+++ b/amaksatov/postgresql/script.sql
@@ -1 +0,0 @@
-SELECT * FROM table3;
\ No newline at end of file

From 036eb440a8f2d7532c81b763c93e9a0de1f1c1b6 Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sat, 10 Jan 2026 20:13:58 +0600
Subject: [PATCH 4/9] fixed

---
 amaksatov/postgresql/OS-329.sql | 2 --
 1 file changed, 2 deletions(-)

diff --git a/amaksatov/postgresql/OS-329.sql b/amaksatov/postgresql/OS-329.sql
index a3d3ea3..3f0f080 100644
--- a/amaksatov/postgresql/OS-329.sql
+++ b/amaksatov/postgresql/OS-329.sql
@@ -213,5 +213,3 @@ VALUES
     '2023-04-03 10:00:00'
 );
 
-
-SELECT * FROM amaksatov.lessons
\ No newline at end of file

From 47599c3420bc1e90222e99a2903b021fa607980b Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sat, 10 Jan 2026 21:24:36 +0600
Subject: [PATCH 5/9] Done

---
 amaksatov/postgresql/OS-330.sql | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)
 create mode 100644 amaksatov/postgresql/OS-330.sql

diff --git a/amaksatov/postgresql/OS-330.sql b/amaksatov/postgresql/OS-330.sql
new file mode 100644
index 0000000..86a034c
--- /dev/null
+++ b/amaksatov/postgresql/OS-330.sql
@@ -0,0 +1,19 @@
+CREATE MATERIALIZED VIEW user_activity_summary AS
+SELECT 
+    u.id AS user_id,
+    u.name,
+    COUNT(DISTINCT e.course_id) AS enrollment_count,
+    COUNT(DISTINCT lv.lesson_id) AS viewed_lessons_count,
+    MAX(lv.viewed_at) AS last_viewed,
+    MIN(lv.viewed_at) AS first_viewed,
+    ROUND (
+        CASE
+            WHEN COUNT(DISTINCT l.id) = 0 THEN NULL
+            ELSE COUNT(DISTINCT lv.lesson_id) * 1.0 / COUNT(DISTINCT l.id) * 100
+        END, 2)::TEXT || '%' AS "engagement_rate"
+FROM amaksatov.users u
+LEFT JOIN enrollments e ON e.user_id = u.id
+LEFT JOIN lessons l ON l.course_id = e.course_id
+LEFT JOIN lesson_views lv ON lv.lesson_id = l.id AND u.id = lv.user_id
+GROUP BY u.id
+HAVING COUNT(e.id) > 0;
\ No newline at end of file

From 43e731927f60fef4ba70b2974dde0c3aff4d79a4 Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sat, 10 Jan 2026 21:26:08 +0600
Subject: [PATCH 6/9] OS-330

---
 amaksatov/postgresql/script.sql | 0
 1 file changed, 0 insertions(+), 0 deletions(-)
 delete mode 100644 amaksatov/postgresql/script.sql

diff --git a/amaksatov/postgresql/script.sql b/amaksatov/postgresql/script.sql
deleted file mode 100644
index e69de29..0000000

From 5edbdc2e8c3b16e144c19aa03d6eeb17a25965b7 Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sun, 11 Jan 2026 16:53:12 +0600
Subject: [PATCH 7/9] Fixed

---
 amaksatov/postgresql/OS-330.sql | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/amaksatov/postgresql/OS-330.sql b/amaksatov/postgresql/OS-330.sql
index 86a034c..beeae0e 100644
--- a/amaksatov/postgresql/OS-330.sql
+++ b/amaksatov/postgresql/OS-330.sql
@@ -6,14 +6,10 @@ SELECT
     COUNT(DISTINCT lv.lesson_id) AS viewed_lessons_count,
     MAX(lv.viewed_at) AS last_viewed,
     MIN(lv.viewed_at) AS first_viewed,
-    ROUND (
-        CASE
-            WHEN COUNT(DISTINCT l.id) = 0 THEN NULL
-            ELSE COUNT(DISTINCT lv.lesson_id) * 1.0 / COUNT(DISTINCT l.id) * 100
-        END, 2)::TEXT || '%' AS "engagement_rate"
+    ROUND (COUNT(DISTINCT lv.lesson_id) * 1.0 / NULLIF(COUNT(DISTINCT l.id), 0) * 100, 2) AS "engagement_rate(%)"
 FROM amaksatov.users u
 LEFT JOIN enrollments e ON e.user_id = u.id
 LEFT JOIN lessons l ON l.course_id = e.course_id
 LEFT JOIN lesson_views lv ON lv.lesson_id = l.id AND u.id = lv.user_id
-GROUP BY u.id
-HAVING COUNT(e.id) > 0;
\ No newline at end of file
+GROUP BY u.id;
+

From 049de3c93a72fbbaab7af5854516cb7dd45cb89f Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sun, 11 Jan 2026 17:47:05 +0600
Subject: [PATCH 8/9] Final fix

---
 amaksatov/postgresql/OS-330.sql | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/amaksatov/postgresql/OS-330.sql b/amaksatov/postgresql/OS-330.sql
index beeae0e..4745707 100644
--- a/amaksatov/postgresql/OS-330.sql
+++ b/amaksatov/postgresql/OS-330.sql
@@ -1,15 +1,16 @@
-CREATE MATERIALIZED VIEW user_activity_summary AS
-SELECT 
-    u.id AS user_id,
-    u.name,
-    COUNT(DISTINCT e.course_id) AS enrollment_count,
-    COUNT(DISTINCT lv.lesson_id) AS viewed_lessons_count,
-    MAX(lv.viewed_at) AS last_viewed,
-    MIN(lv.viewed_at) AS first_viewed,
-    ROUND (COUNT(DISTINCT lv.lesson_id) * 1.0 / NULLIF(COUNT(DISTINCT l.id), 0) * 100, 2) AS "engagement_rate(%)"
-FROM amaksatov.users u
-LEFT JOIN enrollments e ON e.user_id = u.id
-LEFT JOIN lessons l ON l.course_id = e.course_id
-LEFT JOIN lesson_views lv ON lv.lesson_id = l.id AND u.id = lv.user_id
-GROUP BY u.id;
 
+CREATE MATERIALIZED VIEW user_activity_summary AS
+SELECT
+    u.id AS user_id, -- user_id
+    u.name, -- name
+    COUNT(DISTINCT e.course_id) AS enrollment_count, -- кол-во записей на курсы
+    COUNT(DISTINCT lv.lesson_id) AS viewed_lessons_count, -- кол-во просмотренных уроков
+    MAX(lv.viewed_at) AS last_viewed, -- последний просмотр
+    MIN(lv.viewed_at) AS first_viewed, -- первый просмотр
+    ROUND(COUNT(DISTINCT l.course_id) * 100.0 / COUNT(DISTINCT l.id), 2) || '%' AS engagement_rate -- вовлеченность(процент просмотренных/записанным)
+FROM amaksatov.users u -- основная таблица
+JOIN enrollments e ON e.user_id = u.id -- связь users с enrollments
+LEFT JOIN lesson_views lv ON lv.user_id = e.user_id -- связь lessons с lesson_views
+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

From ebe1f007160a424ca17c4f10c7bf2d45019a22d0 Mon Sep 17 00:00:00 2001
From: Azamat <azamatmaksatov911@yandex.com>
Date: Sun, 11 Jan 2026 18:47:48 +0600
Subject: [PATCH 9/9] Full pet-project

---
 amaksatov/postgresql/OS-330.sql | 52 +++++++++++++++++++++++++++++++++
 1 file changed, 52 insertions(+)

diff --git a/amaksatov/postgresql/OS-330.sql b/amaksatov/postgresql/OS-330.sql
index 4745707..9b78b52 100644
--- a/amaksatov/postgresql/OS-330.sql
+++ b/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;