added STEP 1, 3, 4.3

skonev/greenplum/STEP4.3_dm.course_completion_rate.sql

@@ -0,0 +1,39 @@
+/# 
+- ВИТРИНА ДЛЯ АНАЛИЗА КОНВЕРСИИ ПРОХОЖДЕНИЯ КУРСА ПОЛЬЗОВАТЕЛЯМИ
+- ИТОГОВОЕ РАСПРЕДЕЛЕНИЕ ПО (user_id, course_id)
+#/
+
+CREATE MATERIALIZED VIEW dm.course_completion_rate AS
+WITH t1 AS (
+SELECT DISTINCT
+	e.user_id,
+	du.name AS user_name,
+	e.course_id, 
+	dc.title AS course_title,
+	COUNT(DISTINCT dl.lesson_id) AS lessons_in_course
+FROM core.enrollments e
+JOIN core.dim_user du USING (user_id)
+JOIN core.dim_course dc USING (course_id)
+LEFT JOIN core.dim_lesson dl USING (course_id)
+GROUP BY user_id, du.name, course_id, dc.title
+),
+t2 AS (
+SELECT 
+	user_id,
+	course_id,
+	COUNT(lesson_id) AS lessons_viewed
+FROM core.fact_lesson_views
+GROUP BY user_id, course_id
+)
+
+SELECT 
+	t1.user_id,
+	t1.user_name,
+	t1.course_id,
+	t1.course_title,
+	t1.lessons_in_course,
+	COALESCE(t2.lessons_viewed, 0) AS lessons_viewed,
+	COALESCE(ROUND(lessons_viewed::DECIMAL / NULLIF(lessons_in_course, 0), 2), 0) AS completion_rate
+FROM t1 
+LEFT JOIN t2 USING (user_id, course_id)
+DISTRIBUTED BY (user_id, course_id);