timestamp-এ কাজ — now, age, date_trunc, EXTRACT

SELECT now()                                    AS now,
       created_at                              AS ordered_at,
       AGE(created_at)                         AS age,
       created_at::date                        AS day,
       EXTRACT(YEAR FROM created_at)           AS year
FROM orders
ORDER BY created_at DESC
LIMIT 3;

SELECT COUNT(*) AS orders_last_7d
FROM orders
WHERE created_at >= now() - INTERVAL '7 days';

SELECT date_trunc('day', created_at) AS day,
       COUNT(*)                            AS orders
FROM orders
GROUP BY day
ORDER BY day;