题解 | #返回每个订单号各有多少行数#
返回每个订单号各有多少行数
https://www.nowcoder.com/practice/cf1f8d4a514d455aa0468718fb411f41
/*算法顺序是先group by 再 select ，按order_num分组后 count(order_num)就是计算相同order_num出现的次数。*/ select order_num, count(order_num) order_lines from OrderItems group by order_num order by order_lines;
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