sql - 不要在分组依据中包含选择列

Question

这是我的表格(仅包括相关列)

Table: carts
address_id - integer

Table: addresses
name - varchar
phone - varchar

Table: orders
order_number - integer (this is the foreign key for cart table)

我想获取只订购过一次的客户的电话号码，所以我构建了以下查询

select addresses.phone 
from orders 
   inner join carts on orders.order_number = carts.id 
   inner join address on carts.address_id = addresses.id 
group by addresses.phone 
having count(orders.*) = 1;

这很好用!但我还需要选择客户名称和订单号，我将选择语句更新为

select addresses.phone, addresses.name, orders.order_number ...

现在，postgres 敦促我将这些列包含在 GROUP BY 子句中，但这不会返回我想要的结果。

我尝试如下使用子查询，这似乎让我得到了想要的结果

select addresses.phone, (select ad.name from addresses ad where ad.phone = addresses.phone) ...

但是使用子查询是解决这个问题的唯一方法吗？还是有更简单/最佳的方法？

Answer 1

您可以使用 window function 来实现此目的这不需要对所有内容进行分组:

select *
from (
  select addresses.phone, addresses.name, orders.order_number, 
         count(orders.order_number) over (partition by addresses.phone) as cnt
  from orders 
     inner join carts on orders.order_number = carts.id 
     inner join address on carts.address_id = addresses.id 
) t 
where cnt = 1;