无法使用 mongo shell 找到 MongoDB 的正确查询

Question

我一直在尝试获取包含每种药物的最新（根据其成立日期）药房的清单。

以下面文档数组的结果为例：

Output:
Medicine : MedA , Pharmacy : a
Medicine : MedB , Pharmacy : b
Medicine : MedC , Pharmacy : b
Medicine : MedD , Pharmacy : a

[
  {
    "Pharmacy": "a",
    "EstablishedDate": ISODate("2006-10-12"),
    "Medicine": [
      {
        "MedName": "MedA",
        "Quantity": 55
      },
      {
        "MedName": "MedB",
        "Quantity": 34
      },
      {
        "MedName": "MedD",
        "Quantity": 25
      }
    ]
  },
  {
    "Pharmacy": "b",
    "EstablishedDate": ISODate("2015-2-2"),
    "Medicine": [
      {
        "MedName": "MedB",
        "Quantity": 60
      },
      {
        "MedName": "MedC",
        "Quantity": 34
      }
    ]
  }
]

如何解决？

Answer 1

1.Answer 各个药房的所有药品

db.collection.aggregate([
  {
    $unwind: "$Medicine"
  },
  {
    $project: {
      "_id": 0,
      "Medicine": "$Medicine.MedName",
      "Pharmacy": "$Pharmacy"
    }
  }
])

输出

[
  {
    "Medicine": "MedA",
    "Pharmacy": "a"
  },
  {
    "Medicine": "MedB",
    "Pharmacy": "a"
  },
  {
    "Medicine": "MedD",
    "Pharmacy": "a"
  },
  {
    "Medicine": "MedB",
    "Pharmacy": "b"
  },
  {
    "Medicine": "MedC",
    "Pharmacy": "b"
  }
]

参考playground和运行脚本

2.All 有最新药房的药品

db.collection.aggregate([
  {
    $unwind: "$Medicine"
  },
  {
    $sort: {
      EstablishedDate: -1
    }
  },
  {
    $group: {
      _id: "$Medicine.MedName",
      Pharmacy: {
        $first: "$Pharmacy"
      }
    }
  },
  {
    $project: {
      _id: 0,
      "Medicine": "$_id",
      "Pharmacy": "$Pharmacy"
    }
  }
])

输出

[
  {
    "Medicine": "MedA",
    "Pharmacy": "a"
  },
  {
    "Medicine": "MedC",
    "Pharmacy": "b"
  },
  {
    "Medicine": "MedD",
    "Pharmacy": "a"
  },
  {
    "Medicine": "MedB",
    "Pharmacy": "b"
  }
]

分别参考playground和运行脚本

无法使用 mongo shell 找到 MongoDB 的正确查询

Can't find right query for MongoDB using mongo shell

mongoose

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node.js

mongo-shell

mongodb-query