Fungsi Agregat Menengah

Otomatisasi Data Pipeline di Snowflake

Emily Melhuish

Technical Curriculum Developer, Snowflake

Urutan Operasi

Urutan operasi.png

SQL tidak dijalankan sesuai urutan penulisan

Baris: bangun dataset
Grup: ringkas data
Hasil: bentuk output

¹ * Materi Pembelajaran Snowflake

Fungsi Agregat Umum

COUNT(*) / COUNT(DISTINCT col) — total baris; nilai unik
SUM — total kolom
AVG — nilai rata-rata
MIN / MAX — rentang

SELECT COUNT(*) AS total_shipments,
       COUNT(DISTINCT carrier_id) AS unique_carriers,
       SUM(delivery_days) AS total_days,
       AVG(delivery_days) AS avg_days
FROM shipments;

Masalah dengan Banyak Kueri

Kembalikan penggunaan per wilayah dan gudang

SELECT 
region
, warehouse_name
, SUM(credits_used) 
FROM usage 
GROUP BY region, warehouse_name;

Kembalikan subtotal penggunaan per wilayah

SELECT region
, SUM(credits_used) 
FROM usage GROUP BY region;

Kembalikan total penggunaan

SELECT 
SUM(credits_used) 
FROM usage;

GROUPING SETS

Input

SELECT region
, warehouse_name
, SUM(credits_used) AS total 
FROM usage 
GROUP BY GROUPING SETS ( 
  (region, warehouse_name)
  , (region)
  , () 
);

Output

REGION	WAREHOUSE_NAME	TOTAL
EMEA	harbr_wh_prod	1240.50
EMEA	harbr_wh_dev	380.00
EMEA	NULL	1620.50
APAC	harbr_wh_prod	890.25
APAC	NULL	890.25
NULL	NULL	2510.75

Catatan: Beri makna pada NULL melalui pernyataan CASE

ROLLUP

Input

SELECT 
region
, warehouse_name
, SUM(credits_used) AS total 
FROM usage 
GROUP BY ROLLUP (region, warehouse_name);

Output

REGION	WAREHOUSE_NAME	TOTAL
EMEA	harbr_wh_prod	1240.50
EMEA	harbr_wh_dev	380.00
EMEA	NULL	1620.50
APAC	harbr_wh_prod	890.25
APAC	NULL	890.25
NULL	NULL	2510.75

CUBE

Input

SELECT 
region
, warehouse_name
, SUM(credits_used) AS total
FROM usage 
GROUP BY CUBE (region, warehouse_name);

Output

REGION	WAREHOUSE_NAME	TOTAL
EMEA	harbr_wh_prod	1240.50
EMEA	harbr_wh_dev	380.00
EMEA	NULL	1620.50
APAC	harbr_wh_prod	890.25
APAC	NULL	890.25	}
NULL	harbr_wh_prod	2130.75
NULL	harbr_wh_dev	380.00
NULL	NULL	2510.75

GROUPING() dan GROUPING_ID()

SELECT region, warehouse_name, SUM(credits_used) AS total_credits, GROUPING(region) AS is_region_agg, GROUPING(warehouse_name) AS is_wh_agg , 
GROUPING_ID(region, warehouse_name) AS grouping_level 
FROM usage 
GROUP BY ROLLUP (region, warehouse_name);

Tangkapan layar output tabel markdown

Ayo berlatih!

Otomatisasi Data Pipeline di Snowflake