-- 逻辑拆解：连接表，按照商品分组，聚合求销售额，时间条件-2024年上半年(特别注意不能直接用where条件筛选时间，因为这样会变相把LEFT JOIN变成inner join)
SELECT 
    t1.product_id,
    t1.product_name,
    SUM(t1.price * t2.quantity) total_sales
FROM products_underline t1
LEFT JOIN sales_underline t2
ON t1.product_id = t2.product_id
AND t2.sale_month BETWEEN '2024-01' AND '2024-06'
GROUP BY t1.product_id
ORDER BY t1.product_id