题解 | #计算总和#把item_price移到括号外面会报错
计算总和
http://www.nowcoder.com/practice/d8a624021183454586da94d280cc8046
SELECT order_num, SUM(quantity*item_price) AS total_price
FROM OrderItems
GROUP BY order_num
HAVING SUM(quantity*item_price) >= 1000
ORDER BY order_num ASC;
如果把item_price移到括号外面会报错，因为聚合函数的结果乘以一个item_price，它并不知道要乘以哪个item_price。
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