如何在MongoDB中将一个集合与另一个没有关系的集合的对象组合在一起？

db.collection.aggregate([
  {
    $lookup: {
      from: "otherCollection",
      localField: "fieldInCurrentCollection",
      foreignField: "fieldInOtherCollection",
      as: "combinedObjects"
    }
  }
])

db.collection.aggregate([
  {
    $lookup: {
      from: "otherCollection",
      localField: "fieldInCurrentCollection",
      foreignField: "fieldInOtherCollection",
      as: "combinedObjects"
    }
  },
  {
    $project: {
      _id: 0,
      field1: "$fieldInCurrentCollection",
      field2: "$combinedObjects.fieldInOtherCollection"
    }
  }
])