Зачем нужен Data Warehouse

-- На OLTP: 20+ JOIN, нагрузка на продакшн
SELECT u.name, p.category, SUM(oi.price * oi.qty) AS revenue
FROM users u
JOIN orders o ON o.user_id = u.id
JOIN order_items oi ON oi.order_id = o.id
JOIN products p ON p.id = oi.product_id
JOIN categories c ON c.id = p.category_id
WHERE o.created_at BETWEEN '2024-01-01' AND '2024-03-31'
GROUP BY u.name, p.category;

SELECT r.region_name, c.segment, SUM(f.revenue) AS total_revenue
FROM fact_orders f
JOIN dim_region r ON r.region_id = f.region_id
JOIN dim_customer c ON c.customer_id = f.customer_id
WHERE f.channel = 'online'
GROUP BY r.region_name, c.segment;