MongoDb聚合查询三集

Question

我对MongoDB查询和实践mongoDb查询非常陌生。我正在使用这个官方的mongoDb-包。我遵循这个文档 .I有三个数据集合。一个是袋子，一个是卖家，最后一个是衣服。我们的数据架构是当卖方发送带着他/她的信息的布袋时。我们创建了这样的卖方系列：

{   "sellerId": 1234,
    "firstName": "John",
    "lastName": "doe",
    "fullName": "John Doe",
    "email": "john@yahoo.com",
    "bagId": 2224
}

这是包收集

 { 
   "sellerId": 1234
    "bagId": 2224,
    "source" : "fedex"
}

在从准备出售的袋子中挑选布料后，我们创造了布匹收藏。

[
{
    "bagId": 2224,
    "brandName": "Denim",
    "size": "32",
    "clothId": 1244,
    "color": "green",
    "price": 20
},
{
    "bagId": 2224,
    "brandName": "Zara",
    "size": "31",
    "clothId": 1243,
    "color": "red",
    "price": 90
}
]

当布从Shopify卖出去时。我们得到了SKU的数组，这是我们的布匹收藏clothId.

我的目标是，当布被出售时，我们匹配clothId(SKU-ID来自SHOPIFY)查找bagId，从bagId我们将得到卖家的信息。

我的预期结果是

{

    "firstName": "John",
    "lastName": "doe",
    "fullName": "John Doe",
    "email": "john@yahoo.com",
    "bagId": 2224,
    "clothId": 1244 // sold cloth id which I got from Shopify
    "sellerId": 1234
}

我成功地匹配了出售的布id和shopify (SKU-ID)，并获得了包的信息，但我无法弄清楚，如何从bagId获得卖家的信息。

--这是我的代码--布信息和袋子的详细信息，但它并没有给我卖家的信息，只是得到了空数组

const sllerInfo = await client
    .db()
    .collection('clothes')
    .aggregate(
      [
        { $match: { clothId: { '$in': convertInto } } }, // convertInto is arrays of sold clothId which I got from Shopify
        {
          $lookup:
          {
            from: "bags",
            localField: "bagId",
            foreignField: "bagId",
            as: "bags"
          }
        },
        {
          $lookup:
          {
            from: "sellers",
            localField: "sellerId",
            foreignField: "sellerId",
            as: "sellers"
          },
        },
        {
          "$project": {
            "bagId": 1.0,
            "bags.source": 1.0,
            "sellers.firstName": 1.0, // dont get anything
            "sellers.lastName": 1.0,  // dont get anything
            "brand": 1.0
          }
        },
      ]
    ).toArray()

Answer 1

演示- 8HLT1T

您必须使用$unwind，您需要从bags.sellerId获得卖方id

db.clothes.aggregate([
  {
    $match: {
      clothId: {
        "$in": [
          1244,
          1243
        ]
      }
    }
  },
  {
    $lookup: {
      from: "bags",
      localField: "bagId",
      foreignField: "bagId",
      as: "bags"
    }
  },
  {
    $unwind: "$bags" // break into individual documents
  },
  {
    $lookup: {
      from: "sellers",
      localField: "bags.sellerId", // you need to get seller id from bags
      foreignField: "sellerId",
      as: "sellers"
    },
    
  },
  {
    $unwind: "$sellers"  // break into individual documents
  },
  {
    "$project": {
      _id: 0,
      "clothId": 1,
      "sellerId": "$sellers.sellerId",
      "bagId": 1,
      "bags.source": 1,
      "sellers.firstName": 1,
      "sellers.lastName": 1,
      "brand": 1
    }
  }
])

您可以跳过展开，以防您知道查找中会有唯一匹配的元素。

演示- https://mongoplayground.net/p/IP0epMpQ6mE