Print only the newest record for each name – Use SQL Window functions (ROW_NUMBER, RANK, etc.)

Newest record per name: SELECT FROM (SELECT , ROW_NUMBER() OVER (PARTITION BY name ORDER BY created_at DESC) rn FROM t) t2 WHERE rn=1. Or RANK if ties should all be kept. DENSE_RANK for consecutive ranks. Use FIRST_VALUE/LAST_VALUE for single column: SELECT name, FIRST_VALUE(col) OVER (PARTITION BY name ORDER BY ts DESC) FROM t; then GROUP BY or DISTINCT. Why it matters: Design choices compound at scale—wrong approach can cause 100× overhead. Scalability trade-offs: Profile before optimizing; validate on sample then full. Cost implications: Suboptimal choices multiply at billion-row scale.