Ortak tablo ifadeleri

BigQuery'ye Giriş

Matthew Forrest

Field CTO

CTE nedir?

-- WITH anahtar sözcükleri CTE’yi başlatır
WITH our_cte AS (
  SELECT column1, column2
  FROM table
)


/* CTE parantez içindedir ve alttaki ana sorguda 
bir tablo gibi kullanılabilir */
SELECT *
FROM our_cte

Alt sorgular vs. CTE’ler

Alt sorgu

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 yazma

-- Tüm CTE’ler WITH anahtar sözcüğüyle başlar
WITH cte_name AS


-- CTE parantez içindedir
(SELECT col_1, col_2
 FROM tablename WHERE col_1 > 10
)


-- Yeni CTE 'cte_name' yalnızca bu sorgunun kapsamındadır

SELECT * FROM cte_name LIMIT 10

Birden çok CTE kullanma

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

-- Ek CTE’ler WITH anahtar sözcüğünü tekrar etmez, virgülle ayrılır
order_details AS (
SELECT orders.*, details.order_items
FROM ecommerce.ecomm_orders details 
```

CTE’lerle veri filtreleme

WITH filtered_data AS (
  SELECT *
  FROM ecommerce.ecomm_orders
  -- Burada, veriyi CTE içinde filtreliyoruz
  WHERE order_status = 'delivered'
)
SELECT order_id, order_status
FROM filtered_data

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

CTE’lerle sorgu iyileştirme

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’lerle veri birleştirme

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)

Hadi pratik yapalım!

BigQuery'ye Giriş