第四题求好心人帮忙看一下我的代码，GROUP BY聚合的结果不对不知道为啥 SELECT t.product AS 产品, t.所属区间, sum(t.item_id) AS 成交商品数 FROM ( SELECT product, item_id, CASE WHEN price < 500 THEN '(0,500]&(4863)#39;; WHEN price >= 500 AND price < 1000 THEN &#39;[500,1000)&#39; WHEN price >= 1000 AND price < 5000 THEN &#39;[1000,5000)&#39;; ELSE &#39;5000above&#39;; END AS 所属区间 FROM t_item_order ) GROUP BY t.product, t.所属区间 ORDER BY t.product, count(item_id) DESC;