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，购买年份

。

我想构建一个客户对，其中两个客户都需要在同一年度从同一供应商那里购买相同的产品。我在keytool -list -printcert -jarfile yourapkname.apk中使用self-join来做到这一点。但这太慢了。还有其他选择吗？

BigQuery

Answer 1

使用连接语法并为“客户ID”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

您可以使用聚合在单个行中获得满足条件的 all 个客户：

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，即使使用笛卡尔，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也可能会给您带来简化的好处。在下面尝试以下查询，看看它是否比您的基准便宜：

@PreAuthorize("hasRole('ROLE_USER')")

替代自我加入

3 个答案: