SQL Formatting Conventions

SQL is read more than written. A 200-line analytics query is reviewed dozens of times — formatting pays for itself.

Keyword Case

Two camps:

• UPPER: SELECT id FROM users WHERE created_at > NOW()
• lower: select id from users where created_at > now()

UPPER is older but visually noisy. Lower is cleaner with modern syntax highlighting. Pick one team-wide and enforce with a formatter.

Indentation

Align the leading keyword of each clause:

SELECT

    u.id,
    u.email,
    COUNT(o.id) AS order_count
FROM
    users u
    LEFT JOIN orders o ON o.user_id = u.id
WHERE
    u.created_at > NOW() - INTERVAL '30 days'
GROUP BY
    u.id, u.email
HAVING
    COUNT(o.id) > 5
ORDER BY
    order_count DESC
LIMIT 10;

Each major clause starts at column 0. Inner items indent.

Aliases

• Always alias tables in multi-table queries: users u not users
• Alias derived columns explicitly: COUNT(*) AS user_count
• Avoid single-letter aliases that conflict with reserved words

JOIN Style

Always specify the JOIN type. Avoid implicit comma joins:

-- Good

FROM users u
INNER JOIN orders o ON o.user_id = u.id
-- Avoid
FROM users u, orders o WHERE o.user_id = u.id

CTEs Beat Subqueries

WITH active_users AS (

    SELECT id FROM users WHERE last_seen > NOW() - INTERVAL '7 days'
),
recent_orders AS (
    SELECT user_id, COUNT(*) AS n FROM orders WHERE created_at > NOW() - INTERVAL '7 days' GROUP BY user_id
)
SELECT u.id, COALESCE(o.n, 0)
FROM active_users u
LEFT JOIN recent_orders o ON o.user_id = u.id;

CTEs are linear top-to-bottom; nested subqueries are right-to-left and harder to follow.

Trailing vs Leading Commas

Leading commas make adding/removing columns clean and surface mistakes:

SELECT

    id
  , email
  , name
FROM users;

Pure preference; pick one and enforce.

Auto-formatters

• sqlfluff — Python, opinionated, configurable rules
• pg_format — Postgres-aware
• prettier-plugin-sql — for projects already using Prettier

Run on pre-commit; do not let formatting churn dominate code reviews.

Format queries online with the [SQL Formatter](https://sdk.is/sql-formatter).