如何找到平均值最高的三條記錄？

Question

我必須要找到最高平均3個發運國家：

select shipcountry, AVG(freight) as "avgfreight" 
from sales.orders where year(shippeddate)=2007 
group by shipcountry 
order by 2 desc 

我不能夠使用top命令查找前3名的平均水平。任何指針將高度讚賞。

Answer 1

嘗試

set rowcount 3 

select shipcountry, AVG(freight) as "avgfreight" 
from sales.orders where year(shippeddate)=2007 
group by shipcountry 
order by 2 desc 

這將限制行數返回（該連接上執行的每個查詢）。

如果您要重新使用連接（發出更多語句等），您需要在完成後重置rowcount。

例如

set rowcount 3 

select shipcountry, AVG(freight) as "avgfreight" 
from sales.orders where year(shippeddate)=2007 
group by shipcountry 
order by 2 desc 

set rowcount 0 

Answer 2

下面是一個使用子查詢的一種方法：

select top 3 shipcountry, avgfreight 
from (
    select shipcountry, avg(freight) avgfreight 
    from sales.orders 
    where year(shppeddate) = 2007 
    group by shipcountry 
) t 
order by avgfreight desc 

Answer 3

select top 3 shipcountry, AVG(freight) as "avgfreight" 
from sales.orders 
where year(shippeddate)=2007 
group by shipcountry 
order by AVG(freight) desc 

Answer 4

使用CTE

;With cte as (
    select shipcountry, AVG(freight) avgfreight 
    from sales.orders 
    where year(shippeddate)=2007 
    group by shipcountry 
) 
select top(3) shipcountry, avgfreight 
from cte 
order by avgfreight desc 

Answer 5

試試這個：

declare @sales_orders table 
(
    shipcountry varchar(max), 
    freight int, 
    shippeddate datetime 
) 

insert into @sales_orders values 
('India', '2000', dateadd(yy,-6, getutcdate())), 
('India', '2100', dateadd(yy,-6, getutcdate())), 
('India', '2500', dateadd(yy,-6, getutcdate())), 
('SriLanka', '1000', dateadd(yy,-6, getutcdate())), 
('SriLanka', '1500', dateadd(yy,-6, getutcdate())), 
('SriLanka', '1200', dateadd(yy,-6, getutcdate())), 
('China', '500', dateadd(yy,-6, getutcdate())), 
('China', '1000', dateadd(yy,-6, getutcdate())), 
('China', '900', dateadd(yy,-6, getutcdate())), 
('USA', '100', dateadd(yy,-6, getutcdate())), 
('USA', '200', dateadd(yy,-6, getutcdate())), 
('USA', '600', dateadd(yy,-6, getutcdate())) 


;with cte 
as 
(
select shipcountry, AVG(freight) as avgfreight 
from @sales_orders where year(shippeddate)=2007 
group by shipcountry 
) 
select top 3 avgfreight,shipcountry from cte order by avgfreight desc