题解 | #计算总和#

请问一下，为何我将item_price * 移到sum函数外部就会报错运行不了，就像下面这个样子 SELECT order_num, item_price *SUM(quantity) total_price FROM OrderItems GROUP BY order_num HAVING total_price >= 1000 ORDER BY order_num; 报错如下 SQL_ERROR_INFO: "Expression #2 of SELECT list is not in GROUP BY clause and contains nonaggregated column 'OrderItems.item_price' which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by"

小白有点想不懂，请教一下，为什么要用sum，不能直接item_price * quantity，然后group by bu不是会分组后把item_price * quantity汇总吗？