如何从 MongoDB 中获取不同的值？

Question

我是 MongoDB 的新手，很难从那里获得不同的值。

这是集合中的文档，我想通过 "CustomerAccountNo" 来区分（这是重复值 = 165）

   {
        "_id": "5e3eaf3ef5aab73568bd8494",
        "CustomerAccountNo": "123",
        "Customer": "Lucy Thom"
    },
    {
        "_id": "5e3eaf40f5aab73568bd8495",
        "CustomerAccountNo": "325",
        "Customer": "Nick Granger"
    },
    {
        "_id": "5e3eaf42f5aab73568bd8496",
        "CustomerAccountNo": "658",
        "Customer": "Tommy Tee"
    },
    {
        "_id": "5e3eaf44f5aab73568bd8497",
        "CustomerAccountNo": "6513",
        "Customer": "Carlos Nolasco"
    },
    {
        "_id": "5e3eaf49f5aab73568bd8498",
        "CustomerAccountNo": "165",
        "Customer": "Hungarian Pastry shop"
    },
    {
        "_id": "5e4660e9f57ea925a42b4ba2",
        "CustomerAccountNo": "165",
        "Customer": "Hungarian Pastry shop"
    }

并希望输出如下：

    {
        "_id": "5e3eaf3ef5aab73568bd8494",
        "CustomerAccountNo": "123",
        "Customer": "Lucy Thom"
    },
    {
        "_id": "5e3eaf40f5aab73568bd8495",
        "CustomerAccountNo": "325",
        "Customer": "Nick Granger"
    },
    {
        "_id": "5e3eaf42f5aab73568bd8496",
        "CustomerAccountNo": "658",
        "Customer": "Tommy Tee"
    },
    {
        "_id": "5e3eaf44f5aab73568bd8497",
        "CustomerAccountNo": "6513",
        "Customer": "Carlos Nolasco"
    },
    {
        "_id": "5e3eaf49f5aab73568bd8498",
        "CustomerAccountNo": "165",
        "Customer": "Hungarian Pastry shop"
    }

我正在尝试下面的代码来获得上述响应，

collectionName.distinct("CustomerAccountNo") 

或

collectionName.aggregate([
  { $group: { _id: { CustomerAccountNo: "$CustomerAccountNo", Customer: "$Customer" } } }
]);

但是上面的代码都没有按照我的意愿存档正确的响应，我不知道我做错了什么。

Answer 1

这个聚合会得到需要的结果：

db.test.aggregate( [
  { $group: { _id: "$CustomerAccountNo", doc: { $first: "$$ROOT" } } },
  { $replaceRoot: { newRoot: "$doc" } }
] ).pretty()