Запросы - Синтаксис (Task 1 and 2)
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Bonifatsiy
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/* Запросы - Синтаксис*/
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--! Задача 1 !--
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DROP TABLE IF EXISTS users ON CLUSTER clickhouse_cluster;
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CREATE TABLE users
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ON CLUSTER clickhouse_cluster
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(
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user_id UInt32,
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name String,
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age UInt8,
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country String,
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is_active UInt8
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) ENGINE = MergeTree()
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ORDER BY user_id;
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INSERT INTO users VALUES
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(1, 'Ivan', 30, 'RU', 1),
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(2, 'Anna', 25, 'RU', 1),
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(3, 'Petr', 45, 'RU', 0),
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(4, 'Olga', 35, 'RU', 1),
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(5, 'John', 55, 'US', 1),
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(6, 'Alice', 42, 'US', 0),
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(7, 'Tom', 38, 'US', 1),
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(8, 'Lucas', 28, 'BR', 1),
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(9, 'Maria', 60, 'BR', 1),
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(10, 'João', 27, 'BR', 0),
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(11, 'Kenji', 33, 'JP', 1),
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(12, 'Yuki', 29, 'JP', 0),
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(13, 'Chen', 40, 'CN', 1),
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(14, 'Li', 48, 'CN', 1),
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(15, 'Fatima', 31, 'AE', 1),
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(16, 'Ahmed', 36, 'AE', 1),
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(17, 'George', 24, 'US', 1),
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(18, 'Nina', 34, 'RU', 1),
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(19, 'Max', 50, 'DE', 1),
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(20, 'Sophie', 22, 'DE', 0);
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--Получи 10 самых старших активных пользователей.
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SELECT
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user_id,
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name,
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age,
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is_active
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FROM users
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WHERE is_active = true
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ORDER BY age DESC
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LIMIT 10;
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--Выведи пользователей из country = 'RU', отсортированных по имени.
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SELECT
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user_id,
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name,
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country
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FROM users
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WHERE country = 'RU'
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ORDER BY name;
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--Что произойдёт, если написать LIMIT 10 без ORDER BY? Просто выведет 10 случайных активных прользователей без какой либо сортировки.
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SELECT
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user_id,
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name,
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age
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FROM users
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WHERE is_active = true
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LIMIT 10;
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--Посчитай количество пользователей по странам.
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SELECT
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country,
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COUNT(*) as user_country
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FROM users
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GROUP BY country;
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--Для каждой страны выведи минимальный и максимальный возраст.
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SELECT
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country,
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MIN(age) as min_age,
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MAX(age) as max_age
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FROM users
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GROUP BY country
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ORDER BY country;
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--Отсортируй страны по убыванию количества пользователей.
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SELECT
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country,
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COUNT(*) as user_country
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FROM users
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GROUP BY country
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ORDER BY user_country DESC;
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--! Задача 2 !--
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DROP TABLE IF EXISTS dsolovianov.events ON CLUSTER clickhouse_cluster SYNC;
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CREATE TABLE dsolovianov.events ON CLUSTER clickhouse_cluster
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(
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user_id UInt32,
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event_time DateTime,
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event_type String
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)
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ENGINE = ReplicatedMergeTree(
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'/clickhouse/tables/{shard}/dsolovianov/events_v2',
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'{replica}'
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)
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ORDER BY user_id;
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INSERT INTO dsolovianov.events (user_id, event_time, event_type) VALUES
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(1, '2025-07-17 09:00:00', 'click'),
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(1, '2025-07-17 09:05:00', 'view'),
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(1, '2025-07-17 09:10:00', 'purchase'),
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(2, '2025-07-17 10:00:00', 'click'),
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(2, '2025-07-17 10:05:00', 'click'),
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(2, '2025-07-17 11:00:00', 'view'),
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(3, '2025-07-16 12:00:00', 'view'),
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(3, '2025-07-16 12:30:00', 'click'),
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(3, '2025-07-17 08:00:00', 'purchase'),
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(4, '2025-07-17 13:00:00', 'click'),
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(4, '2025-07-17 14:00:00', 'view'),
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(4, '2025-07-17 15:00:00', 'view'),
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(5, '2025-07-16 20:00:00', 'view'),
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(5, '2025-07-17 01:00:00', 'click'),
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(5, '2025-07-17 06:00:00', 'purchase'),
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(6, '2025-07-17 07:30:00', 'view'),
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(6, '2025-07-17 08:45:00', 'click'),
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(7, '2025-07-16 23:59:59', 'click'),
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(7, '2025-07-17 00:01:00', 'purchase'),
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(7, '2025-07-17 10:10:00', 'view');
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--1. Добавь колонку с кумулятивным количеством событий по `user_id` (используй `count() OVER ...`).
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SELECT
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user_id,
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event_time,
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event_type,
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COUNT(*) OVER (PARTITION BY user_id ORDER BY event_time) AS cumulative_events
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FROM dsolovianov.events
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ORDER BY user_id, event_time;
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--2. Сделай аналог ранжирования событий внутри пользователя: `row_number() OVER (PARTITION BY user_id ORDER BY event_time)`
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SELECT
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user_id,
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event_time,
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event_type,
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ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY event_time) AS event_rank
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FROM dsolovianov.events
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ORDER BY user_id, event_rank;
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--3. Что будет, если ты явно задашь `ROWS BETWEEN`? Поддерживается ли?
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--Да, `ROWS BETWEEN` поддерживается:
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SELECT
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user_id,
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event_time,
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event_type,
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-- кумулятивное окно (все предыдущие строки)
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COUNT(*) OVER (PARTITION BY user_id ORDER BY event_time
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ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) AS cumulative_events,
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-- скользящее окно: текущая + 2 предыдущих события
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COUNT(*) OVER (PARTITION BY user_id ORDER BY event_time
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ROWS BETWEEN 2 PRECEDING AND CURRENT ROW) AS last_3_events,
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-- окно: предыдущая + текущая + следующая
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COUNT(*) OVER (PARTITION BY user_id ORDER BY event_time
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ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS prev_curr_next
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FROM dsolovianov.events
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ORDER BY user_id, event_time;
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--4. Сделай `WITH recent_events AS (...)` — все события за последние 24 часа.
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WITH recent_events AS (
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SELECT *
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FROM dsolovianov.events
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WHERE event_time >= '2025-07-16 15:00:00'
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)
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SELECT * FROM recent_events
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ORDER BY event_time DESC;
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--5. Используй CTE, чтобы посчитать топ-5 пользователей по числу этих событий.
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WITH recent_events AS (
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SELECT *
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FROM dsolovianov.events
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WHERE event_time >= '2025-07-16 15:00:00'
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)
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SELECT
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user_id,
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COUNT(*) AS event_count
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FROM recent_events
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GROUP BY user_id
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ORDER BY event_count DESC
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LIMIT 5;
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--6. Добавь второй `WITH` — для маппинга `event_type → category` и используй его в основном запросе.
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WITH
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event_categories AS (
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SELECT
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event_type,
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CASE
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WHEN event_type = 'click' THEN 'engagement'
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WHEN event_type = 'view' THEN 'engagement'
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WHEN event_type = 'purchase' THEN 'conversion'
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ELSE 'other'
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END AS category
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FROM (SELECT DISTINCT event_type FROM dsolovianov.events)
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),
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recent_events AS (
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SELECT *
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FROM dsolovianov.events
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WHERE event_time >= '2025-07-16 15:00:00'
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)
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SELECT
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re.user_id,
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re.event_time,
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re.event_type,
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ec.category,
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ROW_NUMBER() OVER (PARTITION BY re.user_id ORDER BY re.event_time) AS event_rank,
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COUNT(*) OVER (PARTITION BY re.user_id ORDER BY re.event_time) AS cumulative_events
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FROM recent_events re
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LEFT JOIN event_categories ec ON re.event_type = ec.event_type
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ORDER BY re.user_id, re.event_time;
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/*
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Вопрос: поддерживает ли ClickHouse многоуровневые или рекурсивные CTE?
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многоуровневые CTE - да
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рекурсивные CTE - нет в классическом понимании, а скорее в итеративном смысле.
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*/
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