Korszerű Webshop Adatmodell
Entity-Attribute-Value (EAV) Architektúrában

SELECT product_id, sku, name, base_price, stock_qty
FROM products
WHERE is_active = 1
ORDER BY base_price DESC;

SELECT 
    c.name AS kategoria_nev,
    COUNT(p.product_id) AS termek_db,
    MIN(p.base_price) AS legolcsobb_ar_huf,
    MAX(p.base_price) AS legdragabb_ar_huf,
    ROUND(AVG(p.base_price), 2) AS atlagos_ar_huf
FROM categories c
LEFT JOIN products p ON c.category_id = p.category_id
GROUP BY c.category_id, c.name
HAVING termek_db > 0
ORDER BY atlagos_ar_huf DESC;

SELECT 
    o.order_id,
    CONCAT(c.last_name, ' ', c.first_name) AS vasarlo,
    p.name AS termek,
    oi.quantity AS db,
    oi.subtotal AS osszesen,
    COALESCE(pav_color.value_varchar, '-') AS szin,
    CONCAT(COALESCE(pav_storage.value_number, 0), ' GB') AS tarhely
FROM orders o
JOIN customers c ON o.customer_id = c.customer_id
JOIN order_items oi ON o.order_id = oi.order_id
JOIN products p ON oi.product_id = p.product_id
LEFT JOIN product_attribute_values pav_color 
    ON p.product_id = pav_color.product_id 
    AND pav_color.attribute_id = 1
LEFT JOIN product_attribute_values pav_storage 
    ON p.product_id = pav_storage.product_id 
    AND pav_storage.attribute_id = 2
WHERE o.status IN ('paid', 'shipped');

SELECT 
    c.customer_id,
    CONCAT(c.last_name, ' ', c.first_name) AS vasarlo,
    COUNT(o.order_id) AS rendelesek_szama,
    SUM(o.total_amount) AS ossz_koltes
FROM customers c
JOIN orders o ON c.customer_id = o.customer_id
WHERE o.status <> 'cancelled'
GROUP BY c.customer_id, c.last_name, c.first_name
HAVING SUM(o.total_amount) > (
    -- Allekérdezés: rendelések globális átlaga
    SELECT AVG(total_amount) 
    FROM orders 
    WHERE status <> 'cancelled'
)
ORDER BY ossz_koltes DESC;