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-- Запрос 1
SELECT 
    suppliers.name AS поставщик,
    parts.name AS деталь,
    purchase_items.quantity AS количество
FROM purchase_items
JOIN purchases ON purchase_items.purchase_id = purchases.id
JOIN suppliers ON purchases.supplier_id = suppliers.id
JOIN parts ON purchase_items.part_id = parts.id;



-- Запрос 2
SELECT 
    parts.name AS деталь,
    parts.price AS цена,
    SUM(purchase_items.quantity) AS всего_куплено
FROM purchase_items
JOIN parts ON purchase_items.part_id = parts.id
JOIN purchases ON purchase_items.purchase_id = purchases.id
GROUP BY parts.name, parts.price;