选择每个供应商SQL的5个最后订单

Question

我必须计算数据库中每个供应商的最后五个订单的平均数量。我只想要清单上有30个订单的供应商，所以我创建了一个CTE并包含row_number语句以选择最后5个订单，但只接受最后5个订单，而不是每个供应商。这是我的代码：

With MyCTE (VendorID, OrderDate, PurchaseOrderID, SubTotal, RowNumber)
as
(Select poh.VendorID, OrderDate, PurchaseOrderID, round(SubTotal,2) as Subtotal, ROW_NUMBER () over (Partition by VendorID Order by OrderDate desc) as 'RowNumber'
From Purchasing.PurchaseOrderHeader as poh 
Inner join Purchasing.Vendor as pv on poh.VendorID = pv.BusinessEntityID
where PreferredVendorStatus = '0' and ActiveFlag = '1' AND poh.VendorID in 
(select VendorID From Purchasing.PurchaseOrderHeader as poh 
Inner join Purchasing.Vendor as pv on poh.VendorID = pv.BusinessEntityID
group by VendorID
Having count(PurchaseOrderID) >= 30)
)

Select VendorID, AVG(SubTotal) as 'AVG Order',  (Select AVG(Subtotal) From MyCTE Where RowNumber Between 1 And 5) as 'AVG 5 Last Order'
From  MyCTE
group by VendorID

您怎么看？

Answer 1

如果我理解正确，您将尝试获取所有订单超过30的所有客户的平均所有订单的小计和最近5个订单的平均小计。

如果是这种情况，则最近5个订单的平均值不正确。您平均每个客户的最后5个订单。我做了一些改变。请注意，聚合函数将忽略空值。

WITH MyCTE (VendorID, OrderDate, PurchaseOrderID, SubTotal, RowNumber)

AS（SELECT poh.VendorID，订购日期，PurchaseOrderID，ROUND（小计，2）AS小计，ROW_NUMBER（）超过（按供应商ID排序或按OrderDate DESC排序）为“行号”FROM Purchasing.PurchaseOrderHeader AS poh内部加盟采购商AS PV在poh.VendorID = pv.BusinessEntityID上WHERE PreferredVendorStatus ='0'AND ActiveFlag ='1'和poh.VendorID IN（选择供应商IDFROM Purchasing.PurchaseOrderHeader AS poh内部加盟采购商AS PV在poh.VendorID = pv.BusinessEntityID上按供应商ID分组拥有COUNT（PurchaseOrderID）> = 30））

SELECT供应商ID，AVG（小计）AS'AVG订单'，AVG（行编号<= 5时的情况，然后小计ELSE空）AS'AVG 5 Last Order'来自MyCTE按供应商ID分组；