Dmitry Medvedev
64 lines
1.7 KiB
SQL
64 lines
1.7 KiB
SQL
CREATE MATERIALIZED VIEW lesson_popularity_ranking AS
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SELECT
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pl.id AS lesson_id,
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pl.title AS lesson_title,
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pc.id AS course_id,
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pc.title AS course_title,
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total_views_lesson.total_views AS total_views,
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table_unique_viewers.unique_v AS unique_viewers,
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ROUND(AVG(views_one_user_per_one_lesson.views_per_viewer), 2) AS avg_views_per_viewer, --также это можно было посчитать total_views/unique_viewers
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DENSE_RANK() OVER (
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ORDER BY total_views_lesson.total_views DESC NULLS LAST
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) AS popularity_rank,
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ROUND(table_unique_viewers.unique_v * 100.0 / table_enrolled_users.enrolled_to_course, 2) || '%' AS completion_rate
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FROM pet_lessons pl
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LEFT JOIN (
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SELECT
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lesson_id,
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COUNT(*) AS total_views
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FROM pet_lesson_views
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GROUP BY lesson_id
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) AS total_views_lesson
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ON total_views_lesson.lesson_id = pl.id
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LEFT JOIN pet_courses pc
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ON pc.id = pl.course_id
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LEFT JOIN (
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SELECT
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lesson_id,
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COUNT(DISTINCT user_id) AS unique_v
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FROM pet_lesson_views plv
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GROUP BY plv.lesson_id
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) AS table_unique_viewers
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ON table_unique_viewers.lesson_id = pl.id
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LEFT JOIN (
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SELECT
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lesson_id,
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user_id,
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COUNT(*) AS views_per_viewer
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FROM pet_lesson_views plv
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GROUP BY user_id, lesson_id
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ORDER BY user_id, lesson_id
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) AS views_one_user_per_one_lesson
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ON views_one_user_per_one_lesson.lesson_id = pl.id
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LEFT JOIN (
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SELECT
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course_id,
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COUNT(DISTINCT user_id) AS enrolled_to_course
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FROM pet_enrollments pe
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GROUP BY course_id
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) AS table_enrolled_users
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ON table_enrolled_users.course_id = pc.id
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GROUP BY pl.id, pl.title, pc.id, pc.title, total_views_lesson.total_views, table_unique_viewers.unique_v, table_enrolled_users.enrolled_to_course
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ORDER BY lesson_id;
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