Tulis kode yang mudah dibaca

Menerapkan SQL pada Masalah Dunia Nyata

Dmitriy (Dima) Gorenshteyn

Lead Data Scientist, Memorial Sloan Kettering Cancer Center

Gunakan huruf besar untuk perintah SQL

Asli

select 
  title as film_title, 
  description as film_description
from rental as r
join inventory as i
  on r.inventory_id = i.inventory_id
join film as f
  on i.film_id = f.film_id
where f.length > 90
  and f.replacement_cost > 20;

Lebih baik

SELECT 
  title AS film_title, 
  description AS film_description
FROM rental AS r
JOIN inventory AS i
  ON r.inventory_id = i.inventory_id
JOIN film AS f
  ON i.film_id = f.film_id
WHERE f.length > 90
  AND f.replacement_cost > 20;

Gunakan baris baru & indentasi

Asli

SELECT title, description
FROM rental AS r
JOIN inventory AS i
ON r.inventory_id = i.inventory_id
JOIN film AS f ON i.film_id = f.film_id
WHERE f.length > 90 AND f.replacement_cost > 20;

Lebih baik

SELECT title, 
       description 
FROM rental AS r
JOIN inventory AS i
  ON r.inventory_id = i.inventory_id
JOIN film AS f
  ON i.film_id = f.film_id
WHERE f.length > 90
  AND f.replacement_cost > 20;

Gunakan snake_case

Asli

SELECT 
  title expensivelongtitle, 
  description expensivelongdescription
FROM rental AS r
...

Lebih baik

SELECT 
  title expensive_long_title, 
  description expensive_long_description
FROM rental AS r
...

Gunakan IN alih-alih banyak OR

Asli

SELECT 
    address_id,  
    district 
FROM address
WHERE district = 'Texas'
  OR district = 'Bihar'
  OR district = 'Chiba'
  OR district = 'Chiayi'
  OR district = 'Gois';

Lebih baik

SELECT 
    address_id,  
    district 
FROM address
WHERE district IN ('Texas', 'Bihar', 'Chiba', 
                   'Chiayi', 'Gois');

Gunakan BETWEEN jika memungkinkan

Asli

SELECT 
  title, 
  description
FROM film
WHERE replacement_cost > 15
  AND replacement_cost < 25;

Lebih baik

SELECT 
  title, 
  description
FROM film
WHERE replacement_cost BETWEEN 15 AND 25;

Ayo berlatih!

Menerapkan SQL pada Masalah Dunia Nyata