Question

我必须在每年展示托运人最高总成本的情况下进行查询。我的查询现在每年显示每个托运人的总费用。所以在结果中我必须列出年份，每年托运人和总费用。提前致谢。

select year(OrderDate), s.ShipperID, sum(freight) 
from orders o
join shippers s on o.ShipVia = s.ShipperID
group by year(OrderDate),s.ShipperID

Answer 1

Select a.FreightYear, a,ShipperID, a.FreightValue
from
(
    select year(OrderDate) FreightYear, s.ShipperID, sum(freight) FreightValue
    from orders o
    join shippers s on o.ShipVia = s.ShipperID
    group by year(OrderDate),s.ShipperID
) a
inner join
(
    select FreightYear, max(FrieghtTotal) MaxFreight
    from
    (
        select year(OrderDate) FreightYear, s.ShipperID, sum(freight) FreightTotal
        from orders o
        join shippers s on o.ShipVia = s.ShipperID
        group by year(OrderDate),s.ShipperID
    ) x
    group by FreightYear
) max on max.FreightYear = a.FreightYear and max.MaxFreight = a.FreightValue
order by FreightYear

内部查询a是您的原始查询，通过托运人获取运费值。

内部查询max获取每年的最大值，然后查询max加入查询a，将a中的行限制为年份值=年份的最大值。

干杯 -

Answer 2

如果使用窗口函数，它会略微缩短。

select shippers_ranked.OrderYear as OrderYear,
       shippers_ranked.ShipperId as ShipperId,
       shippers_ranked.TotalFreight as TotalFreight
from
(
    select shippers_freight.*, row_number() over (partition by shippers_freight.OrderYear order by shippers_freight.TotalFreight desc) as Ranking
    from
    (
        select year(OrderDate) as OrderYear, 
               s.ShipperID as ShipperId, 
               sum(freight) as TotalFreight
        from orders o
        inner join shippers s on o.ShipVia = s.ShipperID
        group by year(OrderDate), s.ShipperID
    ) shippers_freight
) shippers_ranked
where shippers_ranked.Ranking = 1
order by shippers_ranked.OrderYear
;

如果两个托运人一年拥有相同的TotalFreight，你需要决定你想要发生什么 - 正如上面的代码所示，你将获得一行（非确定性）。如果您想要一行，我会将ShipperId添加到order by子句中的over()，以便您始终获得相同的行。如果在同一个TotalFreight案例中您希望返回多行，请使用dense_rank()而不是row_number()。

查询子查询，每年得1个结果（最大值）

2 个答案: