Reviewed by Aditya Kumar · Last reviewed 2026-03-24
**CTEs:** WITH cte AS (...) SELECT ... FROM cte. Readability, reuse, recursion. **Conditional join:** AND in ON, or CASE in ON. Multiple LEFT JOINs with different conditions. WITH ranked AS ( SELECT *, ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY date DESC) rn FROM...
CTEs: WITH cte AS (...) SELECT ... FROM cte. Readability, reuse, recursion. Conditional join: AND in ON, or CASE in ON. Multiple LEFT JOINs with different conditions.
WITH ranked AS (
SELECT *, ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY date DESC) rn
FROM events
)
SELECT r.*, u.name
FROM ranked r
LEFT JOIN users u ON r.user_id = u.id AND u.status = 'active'
WHERE r.rn = 1;
Red Flag: Nested subqueries when CTE clearer. Pro-Move: 'CTE per logical step—we use for incremental logic (staging → merge).'
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