SELECT
category,
DATE_TRUNC('month', sale_date) AS month,
SUM(quantity) AS sold_quantity,
SUM(total_price) AS revenue
FROM
sales_table
WHERE
discount > 0
GROUP BY
category,
DATE_TRUNC('month', sale_date)
该查询语句使用了聚合函数对商品按照类别和月份进行分组,同时筛选出打折价大于0的商品记录。结果返回每个类别每个月的销售数据,包括销售数量和销售收入。