How to Format & Beautify Complex SQL Queries (JOINs, CTEs & Subqueries)

In database development, unformatted "wall of text" SQL queries hide catastrophic performance bugs: - Accidental `CROSS JOIN` operations caused by missing table join conditions - Duplicate filter predicates inside complex `OR` groups - Inefficient correlated subqueries that should be refactored into Common Table Expressions (`WITH` clauses) When SQL code is structured with standardized vertical alignment and capitalized keywords, spotting query bottlenecks during code reviews becomes trivial.

1. **Uppercase Reserved Keywords:** Keep `SELECT`, `FROM`, `WHERE`, `GROUP BY`, `ORDER BY`, and `HAVING` in uppercase for immediate visual scanning. 2. **One Column Per Line:** Place individual projection columns on their own line with trailing commas. 3. **Dedicated Lines for JOIN Clauses:** Give each `LEFT JOIN` or `INNER JOIN` its own line with the corresponding `ON` predicate indented underneath. 4. **CTE Alignment:** Format `WITH` clauses with explicit indentation so the main query is clearly separated from subquery definitions.

WITH active_monthly_users AS (
  SELECT
    user_id,
    COUNT(session_id) AS total_sessions,
    MAX(last_active_at) AS last_seen
  FROM user_analytics
  WHERE created_at >= '2026-01-01'
  GROUP BY user_id
)
SELECT
  u.id,
  u.username,
  u.email,
  amu.total_sessions,
  amu.last_seen
FROM users u
INNER JOIN active_monthly_users amu
  ON u.id = amu.user_id
WHERE u.status = 'active'
ORDER BY amu.total_sessions DESC
LIMIT 50;