Question

数据库结构：

db={
  "collection": [
    {
      "key": 15,
      "name": "srk",

    },
    {
      "key": 12,
      "name": "suman",

    }
  ],
  "other": [
    {
      "key": 15,
      "name": "miki",
      "category": "dish"
    },
    {
      "key": 15,
      "name": "mira",
      "category": "air"
    },
    {
      "key": 15,
      "name": "manas",
      "category": "air"
    },
    {
      "key": 166,
      "name": "sibu",
      "category": "dish"
    }
  ]
}

我正在尝试查询：

  db.collection.aggregate([
      {
        $lookup: {
          from: "other",
          localField: "key",
          foreignField: "key",
          as: "inventory_docs"
        }
      },
      {
        $match: {
          key: 15,
          { "inventory_docs":
            { category: 'dish'}
          }
        }
      }
    ])

在mongodb中进行查询时，我没有得到结果。

请看看，告诉我查询中我做错了什么地方。

我将关键字与集合中的15个匹配，并将类别与国外集合中的“ Dish”匹配

Answer 1

db.collection.aggregate([
  {
    $lookup: {
      from: "other",
      localField: "key",
      foreignField: "key",
      as: "inventory_docs"
    }
  },
  {
    $unwind: "$inventory_docs"
  },
  {
    $match: {
      key: 15,
      "inventory_docs.category": "dish"
    }
  }
])

Answer 2

尽管您已自行解决问题。但是查询需要优化

如果您先执行“查找”，您将获得"key": 12或所有其他键的数据。

只是为了优化查询：

db.collection.aggregate([
  { 
     $match : {  key: 15 }
  },
 {
  $lookup: {
    from: "other",
    localField: "key",
    foreignField: "key",
    as: "inventory_docs"
 }
},
{
   $unwind: "$inventory_docs"
},
{
  $match: {
     "inventory_docs.category": "dish"
    } 
  }
])

如何使两个集合中的mongodb查找匹配

2 个答案: