Join di Snowflake

Pengantar Snowflake SQL

George Boorman

Senior Curriculum Manager, DataCamp

JOINS

  • INNER JOIN
  • OUTER JOINS
    • LEFT OUTER JOIN atau LEFT JOIN
    • RIGHT OUTER JOIN atau RIGHT JOIN
    • FULL OUTER JOIN atau FULL JOIN
  • CROSS JOINS
  • SELF JOINS
  • NATURAL JOIN
  • LATERAL JOIN
Pengantar Snowflake SQL

Dataset Pizza

Diagram skema basis data Pizza

Pengantar Snowflake SQL

NATURAL JOIN

  • NATURAL JOIN otomatis mencocokkan kolom dan menghapus duplikat

Sintaks:

SELECT ...
FROM <table_one> [
                     {
                       | NATURAL [ { LEFT | RIGHT | FULL } [ OUTER ] ]
                     }
                   ]
                   JOIN <table_two>
[ ... ]
Pengantar Snowflake SQL

NATURAL JOIN

Tanpa NATURAL JOIN

SELECT * 
FROM pizzas AS p 
JOIN  pizza_type AS t 
    ON t.pizza_type_id = p.pizza_type_id

Hasil join tanpa natural join

Dengan NATURAL JOIN

SELECT *
FROM pizzas AS p 
NATURAL JOIN pizza_type AS t

  Hasil join dengan natural join

Pengantar Snowflake SQL

NATURAL JOIN

 

❌ TIDAK BOLEH ❌

select *
FROM pizzas AS p 
NATURAL JOIN pizza_type AS t
    ON  t.pizza_type_id = p.pizza_type_id

Gambar Error Sintaks

Pengantar Snowflake SQL

NATURAL JOIN

$$

✅ BOLEH ✅

  • Klausa WHERE
SELECT *
FROM pizzas AS p 
NATURAL JOIN pizza_type AS t
WHERE pizza_type_id = 'bbq_ckn'
Pengantar Snowflake SQL

LATERAL JOIN

  • LATERAL JOIN: memungkinkan subquery di FROM merujuk kolom dari tabel atau view sebelumnya.

Sintaks:

SELECT ...
FROM <left_hand_expression> , -- 
LATERAL 
(<right_hand_expression>)

  • left_hand_expression - Tabel, view, atau subquery

  • right_hand_expression - Inline view atau subquery

Pengantar Snowflake SQL

LATERAL JOIN dengan subquery

SELECT 
    p.pizza_id, 
    lat.name, 
    lat.category 
FROM pizzas AS p,

LATERAL -- Kata kunci LATERAL
        ( SELECT * 
          FROM pizza_type AS t

         -- Merujuk kolom query luar: p.pizza_type_id
          WHERE p.pizza_type_id = t.pizza_type_id

        ) AS lat
Pengantar Snowflake SQL

Mengapa LATERAL JOIN?

SELECT 
    *
FROM orders AS o,
LATERAL (
   -- Subquery menghitung total_spent
    SELECT 
        SUM(p.price * od.quantity) AS total_spent
    FROM order_details AS od
    JOIN pizzas AS p 
          ON od.pizza_id = p.pizza_id
    WHERE o.order_id = od.order_id
) AS t
ORDER BY o.order_id
Pengantar Snowflake SQL

Ayo berlatih!

Pengantar Snowflake SQL

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