将2个集合合并到一个集合mongoDB中

Question

I have 2 collections in mongoDB

collection 1

  {
    _id : "123",
    name : "ABC1"
  }

collection 2

  {
    _id : "456",
    name : "DEF1"
  }

I'm trying to combine write a query that gives me an output like so

Output

  [
    {
      _id : "123",
      name : "ABC1"
    },
    {
     _id : "456",
     name : "DEF1"
    }
  ]

I've tried lookup but that seems to append 1 collection to the other, I want the collections to be merged like shown in the output. I have looked at the existing solutions on stack overflow and they all suggest using lookup which does not give me the output that I require.

Answer 1

进行两个独立的查询并将它们组合在

const output = [query1, query2];

Answer 2

This can be done through javascript code on mongo shell as follow:

> var all = []; // initialize a variable with empty values

> db.collection1.find().forEach(function (obj) {all.push(obj);}) // push to all from collection 1

> db.collection2.find().forEach(function (obj) {all.push(obj);}) // push to all from collection 2

> printjson(all) // Print all pushed elements 
[
    {
        "_id" : "123",
        "name" : "ABC1"
    },
    {
        "_id" : "456",
        "name" : "DEF1"
    }
]

Hope this will help you. You can perform this on mongo shell.