SQL商品销量排名第二

商品订单表：order_detail

字段：订单号 order_id, 商品ID sku_id，商品销售数量 sku_num 

需求：取商品销量排名第二的商品ID

select b.sku_id from (
    select sku_id,sumsku,row_number over(partition by sku_id order by sumsku desc) num from (
        select sku_id,sum(sku_num) sumsku from order_detail
        group by sku_id
    ) a
) b where b.num = 2