共通テーブル式（CTE）

BigQuery入門

Matthew Forrest

Field CTO

CTE とは？

-- WITH で CTE を開始
WITH our_cte AS (
  SELECT column1, column2
  FROM table
)


/* CTE は括弧内に書き、
下のメインクエリでテーブルのように使える */
SELECT *
FROM our_cte

サブクエリ vs. CTE

サブクエリ

SELECT *
FROM (
  SELECT order_id, status
  FROM ecommerce.ecomm_order_status
) AS subquery

CTE

WITH cte_name AS (
  SELECT order_id, status
  FROM ecommerce.ecomm_order_status
)
SELECT *
FROM cte_name

CTE の書き方

-- すべての CTE は WITH で始まる
WITH cte_name AS


-- CTE は括弧で囲む
(SELECT col_1, col_2
 FROM tablename WHERE col_1 > 10
)


-- 新しい CTE 'cte_name' はこのクエリ内でのみ参照可能

SELECT * FROM cte_name LIMIT 10

複数の CTE を使う

WITH orders AS (
  SELECT order_id, status
  FROM ecommerce.ecomm_order_status
),

-- 追加の CTE は WITH を再使用せず、カンマで区切る
order_details AS (
SELECT orders.*, details.order_items
FROM ecommerce.ecomm_orders details 
```

CTE でデータをフィルタする

WITH filtered_data AS (
  SELECT *
  FROM ecommerce.ecomm_orders
  -- ここでは CTE 内でデータを絞り込みます
  WHERE order_status = 'delivered'
)
SELECT order_id, order_status
FROM filtered_data

| order_id | order_status |
|----------|--------------|
| 1        | delivered    |
| 2        | delivered    |

CTE でクエリを最適化する

WITH precomputed_data AS (
  SELECT order_id, SUM(payment_value) AS total
  FROM ecommerce.ecomm_payments
  GROUP BY order_id
)
SELECT *
FROM precomputed_data
WHERE total > 1000

| order_id | total   |
|----------|---------|
| 1        | 50000   |
| 2        | 8000    |

CTE でデータを結合する

WITH cte1 AS (
  SELECT order_id, status
  FROM ecommerce.ecomm_order_status
),
cte2 AS (
  SELECT order_id, order_items
  FROM ecommerce.ecomm_orders
)
SELECT *
FROM cte1
JOIN cte2 USING (order_id)

Ayo berlatih!

BigQuery入門