MongoDB lookup 1:N

mongodb_lookup_1_to_n.js

// Authors Collection
{
  "_id" : ObjectId("63430b9e73d381100e27b8e9"),
    "name" : "J. K. Rowling",
      "books" : [
        ObjectId("63430b8a73d381100e27b8e7"),
        ObjectId("63430b8a73d381100e27b8e8")
      ]
}
// Books Collection
{
  "_id" : ObjectId("63430b8a73d381100e27b8e7"),
    "name" : "Philosopher's Stone"
},
{
  "_id" : ObjectId("63430b8a73d381100e27b8e8"),
    "name" : "Chamber of Secrets"
}
// Query
db.getCollection("authors").aggregate({
  $lookup: {
    from: "books",
    localField: "books",
    foreignField: "_id",
    as: "books"
  }
})
// Result
{
  "_id" : ObjectId("63430b9e73d381100e27b8e9"),
    "name" : "J. K. Rowling",
      "books" : [{
        "_id": ObjectId("63430b8a73d381100e27b8e7"),
        "name": "Philosopher's Stone"
      },
      {
        "_id": ObjectId("63430b8a73d381100e27b8e8"),
        "name": "Chamber of Secrets"
      }
      ]
}