题解 | 查询出每个品牌在不同月份的总销售额以及购买该品牌商品的用户的平均年龄

SELECT
    o.category_id,
    SUM(o.order_amount) AS total_sales,
    SUM(CASE WHEN c.customer_gender='男' THEN 1 ELSE 0 END) AS male_customers,
    SUM(CASE WHEN c.customer_gender='女' THEN 1 ELSE 0 END) AS female_customers
FROM
    order_details AS o
    INNER JOIN
    customer_info AS c ON o.order_id=c.order_id
WHERE
    o.order_date BETWEEN '2024-01-01' AND '2024-06-30'
GROUP BY
    o.category_id
ORDER BY
    o.category_id;