自联接的替代方案

Question

我有一个表格-供应网络，包括四栏：

CustomerID，SupplierID，Supplier_productID，Purchase_Year

。

我想建立一个客户对，其中两个客户购买同一产品从同一供应商在一个重点年。我用self-join在BigQuery.But中做这件事--太慢了。有别的选择吗？

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

使用联接语法并执行索引CustomerID列

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

您可以使用聚合来获取满足单行条件的所有客户：

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

然后可以使用数组操作获得对：

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，这可能会给您带来简单的好处(即使使用笛卡儿)。试试下面的查询，看看它是否比基线更便宜：

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