Question

我的收藏如下：

{"orderID" : "30688", "region" : "CO", "customerID" : "11396783", "productID" : "13001"}
{"orderID" : "30688", "region" : "CO", "customerID" : "11396783", "productID" : "8002"}
{"orderID" : "30688", "region" : "CO", "customerID" : "11396783", "productID" : "5001"}
{"orderID" : "89765", "region" : "CA", "customerID" : "54157526", "productID" : "7412"}
{"orderID" : "89765", "region" : "CA", "customerID" : "54157526", "productID" : "5198"}
{"orderID" : "21546", "region" : "KA", "customerID" : "20103585", "productID" : "6851"}
{"orderID" : "21546", "region" : "KA", "customerID" : "20103585", "productID" : "7412"}
{"orderID" : "21546", "region" : "KA", "customerID" : "20103585", "productID" : "6987"}
{"orderID" : "21794", "region" : "NY", "customerID" : "78125522", "productID" : "13001"}

我需要计算在特定区域中按customerID分组的唯一订单ID。到目前为止，我已尝试过以下内容：

db.collection.aggregate( [
   { $group:
      {
        _id: { region: "$region", customer:"$customerID"}
      }
   },
   { $match: { region: "KA" } },
   {$group: {_id:1, count: {$sum : 1 }}}
] );

但它返回一个空结果。

Answer 1

您应该在汇总开始时执行match，以确保您只使用该区域的结果

您还应该将$group更改为customer和order，因为匹配已经整理出来自所需区域的内容

然后，您应该使用group使用{$sum:1}计算唯一订单ID的数量，您可以阅读有关其工作原理的here

db.collection.aggregate( [
  { $match: { region: "KA" } },
  { $group:
    {
      _id: { order: "$orderID", customer:"$customerID"}
    }
  },
  {$group: {_id:"$_id.customerID", count: {$sum : 1 }}
]);

MongoDB唯一值按sum排序

1 个答案: