题解 | 每个顾客购买的最新产品名称

SELECT 
    t1.customer_id,
    c.customer_name,
    p.product_name AS latest_order
FROM ( 
    SELECT 
        customer_id,
        MAX(order_date) AS t2
    FROM orders
    GROUP BY customer_id
) t1
JOIN orders o ON o.customer_id = t1.customer_id AND o.order_date = t1.t2
JOIN customers c ON o.customer_id = c.customer_id
JOIN products p ON p.product_id = o.product_id
ORDER BY t1.customer_id;

--T1 只告诉你 “某个客户最后一次下单是哪一天”，但不告诉你 “那一天他买了什么商品”，而 orders 表才存储了「客户 ID、下单日期、商品 ID」的对应关系，因此必须关联 orders 表。