SQL Formatting Standards & Best Practices

Why SQL Formatting Matters

SQL is a declarative language, meaning it details *what* data to retrieve rather than *how* to fetch it. While database engines parse compact, single-line queries with ease, human developers require structured layouts to audit logic, locate joins, and perform optimization.

Rule 1: Capitalize All Keywords

Always capitalize SQL keywords (`SELECT`, `FROM`, `WHERE`, `JOIN`, `GROUP BY`, `ORDER BY`, `AND`, `OR`). Keep tables, columns, and aliases in lowercase or camelCase:

-- Bad Form
select id, username from users where status = 'active';

-- Standard Form
SELECT id, username 
FROM users 
WHERE status = 'active';

Rule 2: Indent Joins and Nesting

Place each join on a new line and align the `ON` condition. Indent nested subqueries or CTEs (Common Table Expressions) by 2 or 4 spaces:

WITH active_orders AS (
  SELECT user_id, SUM(amount) as total
  FROM orders
  WHERE status = 'completed'
  GROUP BY user_id
)
SELECT u.username, o.total
FROM users u
JOIN active_orders o ON u.id = o.user_id;