EXTRACT وDATE_TRUNC وAGE

EXTRACT: استخراج جزء من التاريخ

SELECT EXTRACT(YEAR  FROM created_at) AS yr,
       EXTRACT(MONTH FROM created_at) AS mo,
       EXTRACT(DAY   FROM created_at) AS d,
       EXTRACT(DOW   FROM created_at) AS day_of_week
FROM orders;

أجزاء EXTRACT الشائعة

SELECT EXTRACT(EPOCH FROM (NOW() - created_at)) AS seconds_ago
FROM events;

DATE_TRUNC: التقريب إلى حد

SELECT date_trunc('day',   NOW());   -- 2024-03-15 00:00:00
SELECT date_trunc('week',  NOW());
SELECT date_trunc('month', NOW());
SELECT date_trunc('hour',  NOW());

التقارير المجمّعة حسب الفترات

SELECT date_trunc('month', created_at) AS month,
       SUM(total) AS revenue
FROM orders
GROUP BY 1
ORDER BY 1;

من بداية العام / من بداية الشهر حتى تاريخه

-- This month so far
SELECT SUM(total) FROM orders
WHERE created_at >= date_trunc('month', NOW())
  AND created_at <  date_trunc('month', NOW()) + INTERVAL '1 month';

AGE: فرق يراعي التقويم

SELECT AGE('2024-03-15', '2020-12-01');
-- → '3 years 3 months 14 days'

SELECT EXTRACT(YEAR FROM AGE('2024-03-15', '2020-12-01'));  -- 3

سلوك AGE ذي الوسيطتين

SELECT AGE(birth_date) FROM users LIMIT 5;

منطق يوم الأسبوع

SELECT * FROM orders
WHERE EXTRACT(ISODOW FROM created_at) IN (6, 7);  -- weekend orders

المنطقة الزمنية في EXTRACT

SELECT EXTRACT(HOUR FROM created_at AT TIME ZONE 'UTC') FROM events;
SELECT EXTRACT(HOUR FROM created_at AT TIME ZONE 'Europe/Berlin') FROM events;

الاقتطاع حسب نافذة مخصصة

SELECT to_timestamp(
  floor(EXTRACT(EPOCH FROM created_at) / 300) * 300
) AS bucket_5min,
COUNT(*)
FROM events
GROUP BY 1
ORDER BY 1;

الفهارس الوظيفية للاقتطاع

CREATE INDEX events_day_idx ON events ((date_trunc('day', created_at)));

مراجعة

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