From 4d56aa1f5b92082564bcbb9f02e733447e85b0fc Mon Sep 17 00:00:00 2001
From: Alex <xarlama@bk.ru>
Date: Mon, 23 Feb 2026 15:02:11 +0300
Subject: [PATCH] Pet 6th task completed

---
 aharlamcev/postgresql/Pet-projectsql.sql | 95 +++++++++++++++++++++++-
 1 file changed, 94 insertions(+), 1 deletion(-)

diff --git a/aharlamcev/postgresql/Pet-projectsql.sql b/aharlamcev/postgresql/Pet-projectsql.sql
index a7cee09..1621bf6 100644
--- a/aharlamcev/postgresql/Pet-projectsql.sql
+++ b/aharlamcev/postgresql/Pet-projectsql.sql
@@ -353,7 +353,100 @@ ROUND(100.0 * unique_viewers / enrolled_to_course, 2) as completion_rate
 from lessons_in_courses lic
 join views_cte vc on lic.lesson_id = vc.lesson_id
 ;
-
+-----------------------------------------------------------------------------------------------
+-- 6 Задания Воронка Конверсии
+create materialized view conversion_funnel AS
+with course_lessons as (
+						select c.id as course_id, c.title as course_title,
+						COUNT(l.id) as total_lessons
+						from courses c
+						join lessons l on l.course_id = c.id
+						group by c.id, c.title
+						),
+registered_users as (
+					select COUNT(distinct id) as total_users
+					from users
+					),
+enrolled_users as (
+					select e.course_id, 
+					COUNT(distinct e.user_id) as enrolled_count
+					from enrollments e
+					group by e.course_id
+					),
+started_users as (
+				select l.course_id,
+				COUNT(distinct lv.user_id) as started_count
+				from lessons l
+				join lesson_views lv on l.id = lv.lesson_id
+				group by l.course_id
+				),
+user_progress as (				
+				select l.course_id, lv.user_id,
+				COUNT(distinct lv.lesson_id) as viewed_lessons
+				from lesson_views lv
+				join lessons l on lv.lesson_id = l.id
+				group by l.course_id, lv.user_id
+				),
+mid_progress_users as (
+					select up.course_id,
+					COUNT(distinct up.user_id) as mid_progress_count
+					from user_progress up
+					join course_lessons cl on up.course_id = cl.course_id
+					where up.viewed_lessons >= cl.total_lessons * 0.5
+					group by up.course_id
+					),
+completed_users as (
+					select up.course_id,
+					COUNT(distinct up.user_id) as completed_count
+					from user_progress up
+					join course_lessons cl on up.course_id = cl.course_id
+					where up.viewed_lessons >= cl.total_lessons
+					group by up.course_id
+					),
+funnel_stages as (
+				select cl.course_id, cl.course_title,
+				'registered' as stage_name,
+				ru.total_users as users_count,
+				1 as stage_order
+				from course_lessons cl
+				cross join registered_users ru
+						union all
+				select cl.course_id, cl.course_title,
+				'enrolled' as stage_name,
+				eu.enrolled_count as users_count,
+				2 as stage_order
+				from course_lessons cl
+				left join enrolled_users eu on cl.course_id = eu.course_id
+						union all
+				select cl.course_id, cl.course_title,
+				'started' as stage_name,
+				su.started_count as users_count,
+				3 as stage_order
+				from course_lessons cl
+				left join started_users su on cl.course_id = su.course_id
+						union all
+				select cl.course_id, cl.course_title,
+				'mid_progress' as stage_name,
+				coalesce(mpu.mid_progress_count, 0) as users_count,
+				4 as stage_order
+				from course_lessons cl
+				left join mid_progress_users mpu on cl.course_id = mpu.course_id
+						union all
+				select cl.course_id, cl.course_title,
+				'completed' as stage_name,
+				coalesce(cu.completed_count, 0) as users_count,
+				5 as stage_order
+				from course_lessons cl
+				left join completed_users cu on cl.course_id = cu.course_id
+				)
+	 select course_id, course_title, stage_name, users_count,
+	 ROUND(100.0 * users_count / NULLIF(LAG(users_count) over (partition by course_id order by stage_order), 0), 2) 
+	 as conversion_from_previous,
+	     ROUND(100.0 * users_count / NULLIF(FIRST_VALUE(users_count) over (partition by course_id order by stage_order), 0), 2) 
+	     as conversion_from_start
+	 from funnel_stages
+;
+-- Признаюсь 6-е задание сделал с помощью нейросети, потому что сам вообще никак к нему подобраться не мог.