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Question

我有一個表格供應網絡，其中包括四列：

客戶ID，供應商ID，供應商_產品ID，采購年

。

我想構建一個客戶對，其中兩個客戶都需要在同一個年度內從同一供應商處購買相同的產品。 我在BigQuery使用self-join來完成此操作，但這太慢了。 還有其他選擇嗎？

select distinct
  a.CustomerID as focal_CustomerID,
  b.CustomerID as linked_CustomerID,
  a.Purchase_Year,
  a.Supplier_productID
from 
  supplynetwork as a,
  supplynetwork as b
where 
  a.CustomerID<>b.CustomerID and
  a.Purchase_Year=b.Purchase_Year and
  a.Supplier_productID=b.Supplier_productID and
  a.SupplierID=b.SupplierID

Answer 1

使用聯接語法並為CustomerID列編制索引

select distinct
  a.CustomerID as focal_CustomerID,
  b.CustomerID as linked_CustomerID,
  a.Purchase_Year,
  a.Supplier_productID
from 
  supplynetwork as a join
  supplynetwork as b
  on   
  a.Purchase_Year=b.Purchase_Year and
  a.Supplier_productID=b.Supplier_productID and
  a.SupplierID=b.SupplierID
  where a.CustomerID<>b.CustomerID 

Answer 2

您可以使用聚合在一行中獲取所有滿足條件的客戶：

select Purchase_Year, Supplier_productID, SupplierID,
       array_agg(distinct CustomerID) as customers
from supplynetwork sn
group by Purchase_Year, Supplier_productID, SupplierID;

然后，您可以使用數組操作獲取對：

with pss as (
      select Purchase_Year, Supplier_productID, SupplierID,
             array_agg(distinct CustomerID) as customers
      from supplynetwork sn
      group by Purchase_Year, Supplier_productID, SupplierID
     )
select c1, c2, pss.*
from pss cross join
     unnest(pss.customers) c1 cross join
     unnest(pss.customers) c2
where c1 < c2;

Answer 3

您可以使用CROSS JOIN ，它（即使是笛卡爾的）也可以使您受益於簡單性。 請在下面嘗試以下查詢，看看它是否比您的基准便宜：

select 
   focal_CustomerID, 
   linked_CustomerID, 
   Purchase_Year, 
   Supplier_ProductID 
from (
  select 
     SupplierID, 
     Supplier_ProductID, 
     Purchase_Year, 
     array_agg(distinct CustomerID) as Customers
  from `mydataset.mytable`
  group by 1,2,3
), unnest(Customers) focal_CustomerID
cross join unnest(Customers) linked_CustomerID
where focal_CustomerID != linked_CustomerID