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Question

我有一个表格供应网络，其中包括四列：

客户ID，供应商ID，供应商_产品ID，采购年

。

我想构建一个客户对，其中两个客户都需要在同一个年度内从同一供应商处购买相同的产品。 我在BigQuery使用self-join来完成此操作，但这太慢了。 还有其他选择吗？

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

使用联接语法并为CustomerID列编制索引

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获取所有满足条件的客户：

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

然后，您可以使用数组操作获取对：

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（即使是笛卡尔的）也可以使您受益于简单性。 请在下面尝试以下查询，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