mongodb 查找具有相同键值但不知道值是什么的文档

Question

我在 collection;

中有以下文档

{'po_no': '456', 'amount': 0.1}
{'po_no': '455', 'amount': 0.2}
{'po_no': '454', 'amount': 0.3}
{'po_no': '456', 'amount': 0.4}

我喜欢查找'po_no'具有相同值的文档，但不知道键值是哪个；所以会发现下面的结果；

{'po_no': '456', 'amount': 0.1}
{'po_no': '456', 'amount': 0.4}

Answer 1

您可以使用$group with po_no and then filter out the documents where count is less then 1 using $match

db.collection.aggregate([
  { "$group": {
    "_id": "$po_no",
    "count": { "$sum": 1 },
    "amount": { "$push": "$amount" }
  }},
  { "$match": { "count": { "$gt": 1 }}},
  { "$unwind": "$amount" },
  { "$project" : { "count": 0 }}
])

输出

[
  {
    "_id": "456",
    "amount": 0.1
  },
  {
    "_id": "456",
    "amount": 0.4
  }
]

Answer 2

可以用$group and then check amount $size大于1:

db.col.aggregate([
    {
        $group: {
            _id: "$po_no",
            amount: { $push: "$amount" }
        }
    },
    {
        $match: {
            $expr: {
                $gt: [ { $size: "$amount" }, 1 ]
            }
        }
    },
    {
        $unwind: "$amount"
    },
    {
        $project: {
            _id: 0,
            po_no: "$_id",
            amount: 1
        }
    }
])

MongoDB playground

mongodb 查找具有相同键值但不知道值是什么的文档

mongodb find documents with the same value for a key but do not know what the value is

mongodb

mongo-shell

aggregation-framework