sql - 使用子查询查询，每年有 1 个结果（最大值）

Question

我必须查询我每年显示的托运人总成本最高的地方。我的查询现在显示每个托运人每年的总成本。所以结果我必须有一个年份清单，每年的托运人和总成本。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

如果您使用窗口函数，它会稍微短一些。

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
;

您需要决定如果两个托运人在一年内拥有相同的 TotalFreight，您希望发生什么 - 正如上面的代码所示，您将获得一行（非确定性）。如果您想要一行，我会将 ShipperId 添加到order by子句中over()，以便您始终获得同一行。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().

Answer 2

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是你原来的查询，得到shipper的运费值。

内部查询 max 获取每一年的最大值，然后将查询 max 连接到查询 a 中，将 a 中的行限制为 a year = 为该年的最大值的行。

干杯 -