From ce82641efbca80929de1f86beaf85a7f7452ad46 Mon Sep 17 00:00:00 2001
From: mnoskov <bather.plaint5x@icloud.com>
Date: Sun, 22 Mar 2026 15:08:45 +0300
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---
 .../DQL_materialized_view_conversion_funnel.sql | 114 ++++++++++++++++++
 1 file changed, 114 insertions(+)
 create mode 100644 mnoskov/postgresql/Пет-проект: Онлайн-курсы/2. Создание отчетности (витрин)/DQL_materialized_view_conversion_funnel.sql

diff --git a/mnoskov/postgresql/Пет-проект: Онлайн-курсы/2. Создание отчетности (витрин)/DQL_materialized_view_conversion_funnel.sql b/mnoskov/postgresql/Пет-проект: Онлайн-курсы/2. Создание отчетности (витрин)/DQL_materialized_view_conversion_funnel.sql
new file mode 100644
index 0000000..6b208c0
--- /dev/null
+++ b/mnoskov/postgresql/Пет-проект: Онлайн-курсы/2. Создание отчетности (витрин)/DQL_materialized_view_conversion_funnel.sql	
@@ -0,0 +1,114 @@
+WITH stage_courses AS (
+	-- registered
+	(SELECT
+		0 AS course_id,
+		1 AS stage_id,
+		'registered' AS stage_name,
+		count(DISTINCT u.id) AS users_count
+	FROM
+		users u)
+	UNION ALL
+	-- enrolled
+	(SELECT
+		e.course_id,
+		2 AS stage_id,
+		'enrolled' AS stage_name,
+		count(DISTINCT e.user_id) AS users_count
+	FROM
+		enrollments e
+	GROUP BY
+		e.course_id
+	ORDER BY
+		e.course_id)
+	UNION ALL	
+	-- started
+	(SELECT
+		l.course_id,
+		3 AS stage_id,
+		'started' AS stage_name,
+		count(DISTINCT lv.user_id) AS users_count
+	FROM
+		lessons l
+	JOIN
+		lesson_views lv ON l.id = lv.lesson_id
+	GROUP BY
+		l.course_id
+	ORDER BY
+		l.course_id)
+	UNION ALL
+	-- mid_progress
+	(WITH lessons_mid AS (
+		SELECT
+			l.course_id,
+			ceil(percentile_cont(0.5) WITHIN GROUP (ORDER BY l.id)) AS mid_in_lesson_id
+		FROM
+			lessons l
+		GROUP BY
+			l.course_id
+	)
+	SELECT
+		lm.course_id,
+		4 AS stage_id,
+		'mid_progress' AS stage_name,
+		count(lv.user_id) AS users_count
+	FROM
+		lessons_mid lm
+	LEFT JOIN
+		lesson_views lv ON lm.mid_in_lesson_id = lv.lesson_id
+	GROUP BY
+		lm.course_id, lm.mid_in_lesson_id
+	ORDER BY
+		lm.course_id)
+	UNION ALL
+	-- completed
+	(WITH courses_lessons_id AS (
+		SELECT
+			l.course_id,
+			l.id AS lesson_id
+		FROM
+			lessons l
+		GROUP BY
+			l.course_id, l.id
+	),
+	lessons_numbers AS (
+		SELECT
+			cli.course_id,
+			cli.lesson_id,
+			ROW_NUMBER() OVER(PARTITION BY cli.course_id ORDER BY cli.lesson_id DESC) AS lesson_number
+		FROM
+			courses_lessons_id cli
+	)
+	SELECT
+		ln.course_id,
+		5 AS stage_id,
+		'completed' AS stage_name,
+		count(lv.user_id) AS users_count
+	FROM
+		lessons_numbers ln
+	LEFT JOIN
+		lesson_views lv ON ln.lesson_id = lv.lesson_id
+	WHERE
+		ln.lesson_number = 1
+	GROUP BY
+		ln.course_id, ln.lesson_id
+	ORDER BY
+		ln.course_id)
+)
+SELECT
+	sc.course_id,
+	c.title AS course_title,
+	sc.stage_id,
+	sc.stage_name,
+	sc.users_count,
+	CASE
+		WHEN lag(sc.users_count) OVER (PARTITION BY sc.course_id ORDER BY sc.stage_id) IS NULL THEN 'first stage'
+		WHEN lag(sc.users_count) OVER (PARTITION BY sc.course_id ORDER BY sc.stage_id) = 0 THEN 0::text || '%'
+		WHEN lag(sc.users_count) OVER (PARTITION BY sc.course_id ORDER BY sc.stage_id) IS NOT NULL THEN round((sc.users_count / lag(sc.users_count) OVER (PARTITION BY sc.course_id ORDER BY sc.stage_id)::NUMERIC) * 100, 0)::text || '%'
+	END AS conversion_from_previous,
+	round((sc.users_count / FIRST_VALUE(sc.users_count) OVER (ORDER BY sc.stage_id)::NUMERIC) * 100, 0)::text || '%' AS conversion_from_start
+FROM
+	courses c
+RIGHT JOIN
+	stage_courses sc ON c.id = sc.course_id
+ORDER BY
+	sc.course_id
\ No newline at end of file