Question

我有2个收藏

material_pack

{
  "_id" : ObjectId("5e43bd417b5590b641d2f408"),
  "title" : "untitle",
  "ref" : [ 
    {"id" : ObjectId("5e43bd517b5590b641d2f409")},
    {"id" : ObjectId("5e43bd517b5590b641d2f40a")},
    {"id" : ObjectId("5e43bd517b5590b641d2f40b")}
]

和材料

[
  {
    "_id" : ObjectId("5e43bd517b5590b641d2f409"),
    "mine_type" : "image/gif"
  },
  {
    "_id" : ObjectId("5e43bd517b5590b641d2f40a"),
    "mine_type" : "image/jpeg"
  },
  {
    "_id" : ObjectId("5e43bd517b5590b641d2f40b"),
    "mine_type" : "image/jpeg"
  },
]

我想要的是将他们与此代码结合在一起

db.material_pack.aggregate([
   {
     $lookup:
       {
         from: 'material',
         localField: 'ref.id',
         foreignField: '_id',
         as: "items_document"
       }
  }
])

但items_document字段的结果为[]

我的结果：

{
  "_id" : ObjectId("5e43bd417b5590b641d2f408"),
  "title" : "untitle",
  "content" : "",
  "categories" : [],
  "ref" : [ 
    {
        "id" : ObjectId("5e43bd517b5590b641d2f409")
    }, 
    {
        "id" : ObjectId("5e43bd517b5590b641d2f40a")
    }, 
    {
        "id" : ObjectId("5e43bd517b5590b641d2f40b")
    }
  ],
  "items_document" : [ ]
 }

我想要这样的结果：

{
  "_id" : ObjectId("5e43bd417b5590b641d2f408"),
  "title" : "untitle",
  "content" : "",
  "categories" : [],
  "ref" : [ 
    {
        "id" : ObjectId("5e43bd517b5590b641d2f409")
    }, 
    {
        "id" : ObjectId("5e43bd517b5590b641d2f40a")
    }, 
    {
        "id" : ObjectId("5e43bd517b5590b641d2f40b")
    }
  ],
  "items_document" : [ 
    {
        "_id" : ObjectId("5e43bd517b5590b641d2f409"),
        "mine_type" : "image/gif",
        ...
    }, 
    {
        "_id" : ObjectId("5e43bd517b5590b641d2f40a"),
        "mine_type" : "image/jpeg",
        ...
    }, 
    {
        "_id" : ObjectId("5e43bd517b5590b641d2f40b"),
        "mine_type" : "image/jpeg",
        ...
    }
  ]
}

Answer 1

你好Apiwut Trusphimai，请检查此Mongo Play，它可能会对您有所帮助。我已经使用了您的代码和集合，并且无需对代码进行任何更改，即可很好地查看我给定的链接。

如何在mongodb中加入2个集合

1 个答案: