PROSAGA码农传奇-Mongodb-如何合并mongo内联文档

0# 無口君 | 2019-08-31 10-32

<div class =“post-text”itemprop =“text”>
  <P>
  </p>
  <div class =“snippet”data-lang =“js”data-hide =“false”data-console =“true”data-babel =“false”>
    <div class =“snippet-code”>
       <pre class="snippet-code-js lang-js prettyprint-override">
        <code>
          let fakeArray = [
                    {
                        "field1" : "1",
                        "field2" : [ 
                            {
                                "f1" : "a",
                                "f2" : "b"
                            }, 
                            {
                                "f1" : "aa",
                                "f2" : "bb"
                            }
                        ]
                    },
                    {
                        "field1" : "2",
                        "field2" : [ 
                            {
                                "f1" : "c",
                                "f2" : "d"
                            }, 
                            {
                                "f1" : "cc",
                                "f2" : "dd"
                            }
                        ]
                    }
                ];

let arr = fakeArray.map(el => {
                    return el.field2;
                });

console.log(arr.flat(1));
        </code>
      </pre>
    </DIV>
  </DIV>
  <P>
  </p>
  <P>
    你可以轻松使用像js这样的功能
    <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map" rel="nofollow noreferrer">
      地图
    </A>
     和
    <a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat" rel="nofollow noreferrer">
      平面
    </A>
  </p>
</DIV>

1# 机器设备维修 | 2019-08-31 10-32

<div class =“post-text”itemprop =“text”>
  <P>
    对于输入数据：
  </p>
   <pre>
    <code>
      [
{
    "field1" : "1",
    "field2" : [ 
        {
            "f1" : "a",
            "f2" : "b"
        }, 
        {
            "f1" : "aa",
            "f2" : "bb"
        }
    ]
}
,
{
    "field1" : "2",
    "field2" : [ 
        {
            "f1" : "c",
            "f2" : "d"
        }, 
        {
            "f1" : "cc",
            "f2" : "dd"
        }
    ]
}
]

</code>
  </pre>
  <P>
    使用聚合：
  </p>
   <pre>
    <code>
      [
  {
    "$unwind": "$field2"
  },
  {
    "$group": {
      "_id": "$field2"
    }
  },
   {
     "$replaceRoot": { "newRoot": "$_id" }
   }
]

</code>
  </pre>
  <P>
    生产：
  </p>
   <pre>
    <code>
      [
  {
    "f1": "c",
    "f2": "d"
  },
  {
    "f1": "cc",
    "f2": "dd"
  },
  {
    "f1": "aa",
    "f2": "bb"
  },
  {
    "f1": "a",
    "f2": "b"
  }
]

</code>
  </pre>
  <P>
    你可以在mongoDB游乐场玩这个：
    <a href="https://play.db-ai.co/m/XItsz6BXLQABKlTe" rel="nofollow noreferrer">
      这里
    </A>
  </p>
</DIV>

2# 绵绵 | 2019-08-31 10-32

3# 樱花弄๑•ั็•็ | 2019-08-31 10-32

<div class =“post-text”itemprop =“text”>
  <P>
    你可以尝试使用
     <code>
      $unwind
    </code>
     和a
     <code>
      $project
    </code>
     在聚合查询中：
  </p>
   <pre>
    <code>
      db.test.insertMany([
    { "field1" : "1", "field2" : [ { "f1" : "a", "f2" : "b" }, { "f1" : "aa", "f2" : "bb" } ] },
    { "field1" : "2", "field2" : [ { "f1" : "c", "f2" : "d" }, { "f1" : "cc", "f2" : "dd" } ] }
]);

db.test.aggregate([
    {$unwind: "$field2"},
    {$project: {
        "f1": "$field2.f1",
        "f2": "$field2.f2"
    }}
]);

</code>
  </pre>
  <P>
    这将为您提供以下输出：
  </p>
   <pre>
    <code>
      { "_id" : ObjectId("5c8b70474c52159bf9357567"), "f1" : "a", "f2" : "b" }
{ "_id" : ObjectId("5c8b70474c52159bf9357567"), "f1" : "aa", "f2" : "bb" }
{ "_id" : ObjectId("5c8b70474c52159bf9357568"), "f1" : "c", "f2" : "d" }
{ "_id" : ObjectId("5c8b70474c52159bf9357568"), "f1" : "cc", "f2" : "dd" }

</code>
  </pre>
  <P>
    <a href="https://play.db-ai.co/m/XItxEAgjhgAB8iV6" rel="nofollow noreferrer">
      https://play.db-ai.co/m/XItxEAgjhgAB8iV6
    </A>
  </p>
</DIV>