Question

我是Mongo的新手，我正在尝试从find（）查询中检索具有相同名称的几个特定数据：

让我解释一下 - ＆gt; 用户是具有以下文档的集合：

"linkedaccounts": [
  {
    "accountname": "Rani Charan",
    "accountnumber": "10815748690065",
    "ifsc": "UTIB0001081",
    "virtualid": "taran@xyz",
    "_id": "571488b9720023940539959e",
    "isDefaultReceiving": false,
    "isDefaultFunding": false,
    "isAppEnabled": false,
    "aeba": false,
    "accountsource": 0
  },
  {
    "accountname": "Rani Singh",
    "accountnumber": "01316366360080",
    "virtualid": "ranisingh@xyz",
    "_id": "571488b972002394053995a0",
    "ifsc": "UTIB0000131",
    "isDefaultReceiving": false,
    "isDefaultFunding": true,
    "isAppEnabled": true,
    "aeba": false,
    "accountsource": 0
  },
  {
    "accountname": "Rani K Singh",
    "accountnumber": "07916956560873",
    "virtualid": "ranik@xyz",
    "_id": "571488b9720023940539959f",
    "ifsc": "UTIB0000791",
    "isDefaultReceiving": true,
    "isDefaultFunding": false,
    "isAppEnabled": true,
    "aeba": false,
    "accountsource": 0
  }
]

现在我想获取虚拟身份证为“ranisingh @ xyz”的帐号和ifsc代码。我能够使用此查询获得一些过滤数据：

db.users.find(
         {"linkedaccounts.virtualid": "ranik@xyz"}, 
         {_id: 0, 'linkedaccounts.accountnumber': 1,'linkedaccounts.ifsc': 1})

但结果我得到所有三个帐号和ifsc代码。像这样： -

{
    "linkedaccounts" : [
            {
                    "accountnumber" : "10815748690065",
                    "ifsc" : "UTIB0001081"
            },
            {
                    "accountnumber" : "01316366360080",
                    "ifsc" : "UTIB0000131"
            },
            {
                    "accountnumber" : "07916956560873",
                    "ifsc" : "UTIB0000791"
            }
    ]}

所以现在我想只打印一个帐号和ifsc代码，其中包含“ranisingh @ xyz”。

Answer 1

你可以使用$ slice从数组中获取第一个元素：

   db.users.aggregate([
   {$unwind:"$linkedaccounts"},
   {$match:{"linkedaccounts.virtualid":"ranik@xyz"}},
   {$project:{
       _id:0,
       linkedaccounts:
            {accountnumber:"$linkedaccounts.accountnumber",
                      ifsc:"$linkedaccounts.ifsc"}       
       }}
   ])

但要重塑文档，您需要使用这样的聚合：

convert score.jpg -rotate 90 -blur 0x2 -threshold 50% result.png

Answer 2

您可以使用“位置$运算符”使其仅返回匹配的子文档，而不是数组中的所有子文档。试试这个：

db.users.find(
  {"linkedaccounts.virtualid": "ranik@xyz"} ,
  {
    _id: 0, 
    'linkedaccounts.$.accountnumber': 1,
    'linkedaccounts.$.ifsc': 1
   }
);

这应该只返回匹配的子文档，如下所示：

{
  _id: ObjectId("564b16849408a50b00ec235e"),
  "linkedaccounts" : [
    {
      "accountnumber" : "07916956560873",
      "ifsc" : "UTIB0000791"
    }
  ]
}

参考：https://docs.mongodb.org/manual/reference/operator/projection/positional/#proj.S

更新回复评论：这不起作用，因为此类查询仅限于使用位置$运算符。我建议改用聚合管道。

MongoDB：仅检索特定记录

2 个答案: