PostgreSQL GROUP BY
GURUH BO‘YICHA
GROUP BY bandi bir xil qiymatlarga ega bo‘lgan qatorlarni “har bir mamlakatdagi mijozlar sonini topish” kabi jamlama qatorlarga guruhlaydi.
GROUP BY bandi ko‘pincha natijalar to‘plamini bir yoki bir nechta ustunlar bo‘yicha guruhlash uchun COUNT(), MAX(), MIN(), SUM(), AVG() kabi jamlash funksiyalari bilan ishlatiladi.
Misol
Har bir mamlakatdagi mijozlar sonini ko‘rsatadi:
SELECT COUNT(customer_id), country
FROM customers
GROUP BY country;
Misolni ishga tushirish »
JOIN bilan GURUHLASH
Quyidagi SQL operatorida har bir mijoz tomonidan qilingan buyurtmalar soni ko‘rsatilgan:
Misol
SELECT customers.customer_name, COUNT(orders.order_id)
FROM orders
LEFT JOIN customers ON orders.customer_id = customers.customer_id
GROUP BY customer_name;
Misolni ishga tushirish »
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